Python2/PyMuPDF: mupdf-source/thirdparty/leptonica/src/compare.c comparison

comparison mupdf-source/thirdparty/leptonica/src/compare.c @ 2:b50eed0cc0ef upstream

ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.

author	Franz Glasner <fzglas.hg@dom66.de>
date	Mon, 15 Sep 2025 11:43:07 +0200
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comparison

equal deleted inserted replaced

-:1d09e1dec1d9
+:b50eed0cc0ef
+/*====================================================================*
+-  Copyright (C) 2001 Leptonica.  All rights reserved.
+-
+-  Redistribution and use in source and binary forms, with or without
+-  modification, are permitted provided that the following conditions
+-  are met:
+-  1. Redistributions of source code must retain the above copyright
+-     notice, this list of conditions and the following disclaimer.
+-  2. Redistributions in binary form must reproduce the above
+-     copyright notice, this list of conditions and the following
+-     disclaimer in the documentation and/or other materials
+-     provided with the distribution.
+-
+-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+-  ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+-  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+-  A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL ANY
+-  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+-  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+-  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+-  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+-  OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+-  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+-  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*====================================================================*/
+/*!
+* \file compare.c
+* <pre>
+*
+*      Test for pix equality
+*           l_int32     pixEqual()
+*           l_int32     pixEqualWithAlpha()
+*           l_int32     pixEqualWithCmap()
+*           l_int32     cmapEqual()
+*           l_int32     pixUsesCmapColor()
+*
+*      Binary correlation
+*           l_int32     pixCorrelationBinary()
+*
+*      Difference of two images of same size
+*           l_int32     pixDisplayDiff()
+*           l_int32     pixDisplayDiffBinary()
+*           l_int32     pixCompareBinary()
+*           l_int32     pixCompareGrayOrRGB()
+*           l_int32     pixCompareGray()
+*           l_int32     pixCompareRGB()
+*           l_int32     pixCompareTiled()
+*
+*      Other measures of the difference of two images of the same size
+*           NUMA       *pixCompareRankDifference()
+*           l_int32     pixTestForSimilarity()
+*           l_int32     pixGetDifferenceStats()
+*           NUMA       *pixGetDifferenceHistogram()
+*           l_int32     pixGetPerceptualDiff()
+*           l_int32     pixGetPSNR()
+*
+*      Comparison of photo regions by histogram
+*           l_int32     pixaComparePhotoRegionsByHisto()  -- top-level
+*           l_int32     pixComparePhotoRegionsByHisto()  -- top-level for 2
+*           l_int32     pixGenPhotoHistos()
+*           PIX        *pixPadToCenterCentroid()
+*           l_int32     pixCentroid8()
+*           l_int32     pixDecideIfPhotoImage()
+*       static l_int32  findHistoGridDimensions()
+*           l_int32     compareTilesByHisto()
+*
+*           l_int32     pixCompareGrayByHisto()  -- top-level for 2
+*       static l_int32  pixCompareTilesByHisto()
+*           l_int32     pixCropAlignedToCentroid()
+*
+*           l_uint8    *l_compressGrayHistograms()
+*           NUMAA      *l_uncompressGrayHistograms()
+*
+*      Translated images at the same resolution
+*           l_int32     pixCompareWithTranslation()
+*           l_int32     pixBestCorrelation()
+*
+*  For comparing images using tiled histograms, essentially all the
+*  computation goes into deciding if a region of an image is a photo,
+*  whether that photo region is amenable to similarity measurements
+*  using histograms, and finally the calculation of the gray histograms
+*  for each of the tiled regions.  The actual comparison is essentially
+*  instantaneous.  Therefore, with a large number of images to compare
+*  with each other, it is important to first calculate the histograms
+*  for each image.  Then the comparisons, which go as the square of the
+*  number of images, actually takes no time.
+*
+*  A high level function that takes a pixa of images and does
+*  all comparisons, pixaComparePhotosByHisto(), uses this split
+*  approach.  It pads the images so that the centroid is in the center,
+*  which will allow the tiles to be better aligned.
+*
+*  For testing purposes, two functions are given that do all the work
+*  to compare just two photo regions:
+*    *  pixComparePhotoRegionsByHisto() uses the split approach, qualifying
+*       the images first with pixGenPhotoHistos(), and then comparing
+*       with compareTilesByHisto().
+*    *  pixCompareGrayByHisto() aligns the two images by centroid
+*       and calls pixCompareTilesByHisto() to generate the histograms
+*       and do the comparison.
+*
+* </pre>
+*/
+#ifdef HAVE_CONFIG_H
+#include <config_auto.h>
+#endif  /* HAVE_CONFIG_H */
+#include <string.h>
+#include <math.h>
+#include "allheaders.h"
+/* Small enough to consider equal to 0.0, for plot output */
+static const l_float32  TINY = 0.00001f;
+static l_ok findHistoGridDimensions(l_int32 n, l_int32 w, l_int32 h,
+l_int32 *pnx, l_int32 *pny, l_int32 debug);
+static l_ok pixCompareTilesByHisto(PIX *pix1, PIX *pix2, l_int32 maxgray,
+l_int32 factor, l_int32 n,
+l_float32 *pscore, PIXA *pixadebug);
+/*------------------------------------------------------------------*
+*                        Test for pix equality                     *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixEqual()
+*
+* \param[in]    pix1
+* \param[in]    pix2
+* \param[out]   psame  1 if same; 0 if different
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) Equality is defined as having the same pixel values for
+*          each respective image pixel.
+*      (2) This works on two pix of any depth.  If one or both pix
+*          have a colormap, the depths can be different and the
+*          two pix can still be equal.
+*      (3) This ignores the alpha component for 32 bpp images.
+*      (4) If both pix have colormaps and the depths are equal,
+*          use the pixEqualWithCmap() function, which does a fast
+*          comparison if the colormaps are identical and a relatively
+*          slow comparison otherwise.
+*      (5) In all other cases, any existing colormaps must first be
+*          removed before doing pixel comparison.  After the colormaps
+*          are removed, the resulting two images must have the same depth.
+*          The "lowest common denominator" is RGB, but this is only
+*          chosen when necessary, or when both have colormaps but
+*          different depths.
+*      (6) For images without colormaps that are not 32 bpp, all bits
+*          in the image part of the data array must be identical.
+* </pre>
+*/
+l_ok
+pixEqual(PIX      *pix1,
+PIX      *pix2,
+l_int32  *psame)
+{
+return pixEqualWithAlpha(pix1, pix2, 0, psame);
+}
+/*!
+* \brief   pixEqualWithAlpha()
+*
+* \param[in]    pix1
+* \param[in]    pix2
+* \param[in]    use_alpha   1 to compare alpha in RGBA; 0 to ignore
+* \param[out]   psame       1 if same; 0 if different
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) See notes in pixEqual().
+*      (2) This is more general than pixEqual(), in that for 32 bpp
+*          RGBA images, where spp = 4, you can optionally include
+*          the alpha component in the comparison.
+* </pre>
+*/
+l_ok
+pixEqualWithAlpha(PIX      *pix1,
+PIX      *pix2,
+l_int32   use_alpha,
+l_int32  *psame)
+{
+l_int32    w1, h1, d1, w2, h2, d2, wpl1, wpl2;
+l_int32    spp1, spp2, i, j, color, mismatch, opaque;
+l_int32    fullwords, linebits, endbits;
+l_uint32   endmask, wordmask;
+l_uint32  *data1, *data2, *line1, *line2;
+PIX       *pixs1, *pixs2, *pixt1, *pixt2, *pixalpha;
+PIXCMAP   *cmap1, *cmap2;
+if (!psame)
+return ERROR_INT("psame not defined", __func__, 1);
+*psame = 0;  /* init to not equal */
+if (!pix1 || !pix2)
+return ERROR_INT("pix1 and pix2 not both defined", __func__, 1);
+pixGetDimensions(pix1, &w1, &h1, &d1);
+pixGetDimensions(pix2, &w2, &h2, &d2);
+if (w1 != w2 || h1 != h2) {
+L_INFO("pix sizes differ\n", __func__);
+return 0;
+}
+/* Suppose the use_alpha flag is true.
+* If only one of two 32 bpp images has spp == 4, we call that
+* a "mismatch" of the alpha component.  In the case of a mismatch,
+* if the 4 bpp pix does not have all alpha components opaque (255),
+* the images are not-equal.  However if they are all opaque,
+* this image is equivalent to spp == 3, so we allow the
+* comparison to go forward, testing only for the RGB equality. */
+spp1 = pixGetSpp(pix1);
+spp2 = pixGetSpp(pix2);
+mismatch = 0;
+if (use_alpha && d1 == 32 && d2 == 32) {
+mismatch = ((spp1 == 4 && spp2 != 4) || (spp1 != 4 && spp2 == 4));
+if (mismatch) {
+pixalpha = (spp1 == 4) ? pix1 : pix2;
+pixAlphaIsOpaque(pixalpha, &opaque);
+if (!opaque) {
+L_INFO("just one pix has a non-opaque alpha layer\n", __func__);
+return 0;
+}
+}
+}
+cmap1 = pixGetColormap(pix1);
+cmap2 = pixGetColormap(pix2);
+if (!cmap1 && !cmap2 && (d1 != d2) && (d1 == 32 || d2 == 32)) {
+L_INFO("no colormaps, pix depths unequal, and one of them is RGB\n",
+__func__);
+return 0;
+}
+if (cmap1 && cmap2 && (d1 == d2))   /* use special function */
+return pixEqualWithCmap(pix1, pix2, psame);
+/* Must remove colormaps if they exist, and in the process
+* end up with the resulting images having the same depth. */
+if (cmap1 && !cmap2) {
+pixUsesCmapColor(pix1, &color);
+if (color && d2 <= 8)  /* can't be equal */
+return 0;
+if (d2 < 8)
+pixs2 = pixConvertTo8(pix2, FALSE);
+else
+pixs2 = pixClone(pix2);
+if (d2 <= 8)
+pixs1 = pixRemoveColormap(pix1, REMOVE_CMAP_TO_GRAYSCALE);
+else
+pixs1 = pixRemoveColormap(pix1, REMOVE_CMAP_TO_FULL_COLOR);
+} else if (!cmap1 && cmap2) {
+pixUsesCmapColor(pix2, &color);
+if (color && d1 <= 8)  /* can't be equal */
+return 0;
+if (d1 < 8)
+pixs1 = pixConvertTo8(pix1, FALSE);
+else
+pixs1 = pixClone(pix1);
+if (d1 <= 8)
+pixs2 = pixRemoveColormap(pix2, REMOVE_CMAP_TO_GRAYSCALE);
+else
+pixs2 = pixRemoveColormap(pix2, REMOVE_CMAP_TO_FULL_COLOR);
+} else if (cmap1 && cmap2) {  /* depths not equal; use rgb */
+pixs1 = pixRemoveColormap(pix1, REMOVE_CMAP_TO_FULL_COLOR);
+pixs2 = pixRemoveColormap(pix2, REMOVE_CMAP_TO_FULL_COLOR);
+} else {  /* no colormaps */
+pixs1 = pixClone(pix1);
+pixs2 = pixClone(pix2);
+}
+/* OK, we have no colormaps, but the depths may still be different */
+d1 = pixGetDepth(pixs1);
+d2 = pixGetDepth(pixs2);
+if (d1 != d2) {
+if (d1 == 16 || d2 == 16) {
+L_INFO("one pix is 16 bpp\n", __func__);
+pixDestroy(&pixs1);
+pixDestroy(&pixs2);
+return 0;
+}
+pixt1 = pixConvertLossless(pixs1, 8);
+pixt2 = pixConvertLossless(pixs2, 8);
+if (!pixt1 || !pixt2) {
+L_INFO("failure to convert to 8 bpp\n", __func__);
+pixDestroy(&pixs1);
+pixDestroy(&pixs2);
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return 0;
+}
+} else {
+pixt1 = pixClone(pixs1);
+pixt2 = pixClone(pixs2);
+}
+pixDestroy(&pixs1);
+pixDestroy(&pixs2);
+/* No colormaps, equal depths; do pixel comparisons */
+d1 = pixGetDepth(pixt1);
+d2 = pixGetDepth(pixt2);
+wpl1 = pixGetWpl(pixt1);
+wpl2 = pixGetWpl(pixt2);
+data1 = pixGetData(pixt1);
+data2 = pixGetData(pixt2);
+if (d1 == 32) {  /* test either RGB or RGBA pixels */
+if (use_alpha && !mismatch)
+wordmask = (spp1 == 3) ? 0xffffff00 : 0xffffffff;
+else
+wordmask = 0xffffff00;
+for (i = 0; i < h1; i++) {
+line1 = data1 + wpl1 * i;
+line2 = data2 + wpl2 * i;
+for (j = 0; j < wpl1; j++) {
+if ((*line1 ^ *line2) & wordmask) {
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return 0;
+}
+line1++;
+line2++;
+}
+}
+} else {  /* all bits count */
+linebits = d1 * w1;
+fullwords = linebits / 32;
+endbits = linebits & 31;
+endmask = (endbits == 0) ? 0 : (0xffffffff << (32 - endbits));
+for (i = 0; i < h1; i++) {
+line1 = data1 + wpl1 * i;
+line2 = data2 + wpl2 * i;
+for (j = 0; j < fullwords; j++) {
+if (*line1 ^ *line2) {
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return 0;
+}
+line1++;
+line2++;
+}
+if (endbits) {
+if ((*line1 ^ *line2) & endmask) {
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return 0;
+}
+}
+}
+}
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+*psame = 1;
+return 0;
+}
+/*!
+* \brief   pixEqualWithCmap()
+*
+* \param[in]    pix1
+* \param[in]    pix2
+* \param[out]   psame
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This returns same = TRUE if the images have identical content.
+*      (2) Both pix must have a colormap, and be of equal size and depth.
+*          If these conditions are not satisfied, it is not an error;
+*          the returned result is same = FALSE.
+*      (3) We then check whether the colormaps are the same; if so,
+*          the comparison proceeds 32 bits at a time.
+*      (4) If the colormaps are different, the comparison is done by
+*          slow brute force.
+* </pre>
+*/
+l_ok
+pixEqualWithCmap(PIX      *pix1,
+PIX      *pix2,
+l_int32  *psame)
+{
+l_int32    d, w, h, wpl1, wpl2, i, j, linebits, fullwords, endbits;
+l_int32    rval1, rval2, gval1, gval2, bval1, bval2, samecmaps;
+l_uint32   endmask, val1, val2;
+l_uint32  *data1, *data2, *line1, *line2;
+PIXCMAP   *cmap1, *cmap2;
+if (!psame)
+return ERROR_INT("&same not defined", __func__, 1);
+*psame = 0;
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+if (pixSizesEqual(pix1, pix2) == 0)
+return 0;
+cmap1 = pixGetColormap(pix1);
+cmap2 = pixGetColormap(pix2);
+if (!cmap1 || !cmap2) {
+L_INFO("both images don't have colormap\n", __func__);
+return 0;
+}
+pixGetDimensions(pix1, &w, &h, &d);
+if (d != 1 && d != 2 && d != 4 && d != 8) {
+L_INFO("pix depth not in {1, 2, 4, 8}\n", __func__);
+return 0;
+}
+cmapEqual(cmap1, cmap2, 3, &samecmaps);
+if (samecmaps == TRUE) {  /* colormaps are identical; compare by words */
+linebits = d * w;
+wpl1 = pixGetWpl(pix1);
+wpl2 = pixGetWpl(pix2);
+data1 = pixGetData(pix1);
+data2 = pixGetData(pix2);
+fullwords = linebits / 32;
+endbits = linebits & 31;
+endmask = (endbits == 0) ? 0 : (0xffffffff << (32 - endbits));
+for (i = 0; i < h; i++) {
+line1 = data1 + wpl1 * i;
+line2 = data2 + wpl2 * i;
+for (j = 0; j < fullwords; j++) {
+if (*line1 ^ *line2)
+return 0;
+line1++;
+line2++;
+}
+if (endbits) {
+if ((*line1 ^ *line2) & endmask)
+return 0;
+}
+}
+*psame = 1;
+return 0;
+}
+/* Colormaps aren't identical; compare pixel by pixel */
+for (i = 0; i < h; i++) {
+for (j = 0; j < w; j++) {
+pixGetPixel(pix1, j, i, &val1);
+pixGetPixel(pix2, j, i, &val2);
+pixcmapGetColor(cmap1, val1, &rval1, &gval1, &bval1);
+pixcmapGetColor(cmap2, val2, &rval2, &gval2, &bval2);
+if (rval1 != rval2 || gval1 != gval2 || bval1 != bval2)
+return 0;
+}
+}
+*psame = 1;
+return 0;
+}
+/*!
+* \brief   cmapEqual()
+*
+* \param[in]    cmap1
+* \param[in]    cmap2
+* \param[in]    ncomps  3 for RGB, 4 for RGBA
+* \param[out]   psame
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This returns %same = TRUE if the colormaps have identical entries.
+*      (2) If %ncomps == 4, the alpha components of the colormaps are also
+*          compared.
+* </pre>
+*/
+l_ok
+cmapEqual(PIXCMAP  *cmap1,
+PIXCMAP  *cmap2,
+l_int32   ncomps,
+l_int32  *psame)
+{
+l_int32  n1, n2, i, rval1, rval2, gval1, gval2, bval1, bval2, aval1, aval2;
+if (!psame)
+return ERROR_INT("&same not defined", __func__, 1);
+*psame = FALSE;
+if (!cmap1)
+return ERROR_INT("cmap1 not defined", __func__, 1);
+if (!cmap2)
+return ERROR_INT("cmap2 not defined", __func__, 1);
+if (ncomps != 3 && ncomps != 4)
+return ERROR_INT("ncomps not 3 or 4", __func__, 1);
+n1 = pixcmapGetCount(cmap1);
+n2 = pixcmapGetCount(cmap2);
+if (n1 != n2) {
+L_INFO("colormap sizes are different\n", __func__);
+return 0;
+}
+for (i = 0; i < n1; i++) {
+pixcmapGetRGBA(cmap1, i, &rval1, &gval1, &bval1, &aval1);
+pixcmapGetRGBA(cmap2, i, &rval2, &gval2, &bval2, &aval2);
+if (rval1 != rval2 || gval1 != gval2 || bval1 != bval2)
+return 0;
+if (ncomps == 4 && aval1 != aval2)
+return 0;
+}
+*psame = TRUE;
+return 0;
+}
+/*!
+* \brief   pixUsesCmapColor()
+*
+* \param[in]    pixs     any depth, colormap
+* \param[out]   pcolor   TRUE if color found
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This returns color = TRUE if three things are obtained:
+*          (a) the pix has a colormap
+*          (b) the colormap has at least one color entry
+*          (c) a color entry is actually used
+*      (2) It is used in pixEqual() for comparing two images, in a
+*          situation where it is required to know if the colormap
+*          has color entries that are actually used in the image.
+* </pre>
+*/
+l_ok
+pixUsesCmapColor(PIX      *pixs,
+l_int32  *pcolor)
+{
+l_int32   n, i, rval, gval, bval, numpix;
+NUMA     *na;
+PIXCMAP  *cmap;
+if (!pcolor)
+return ERROR_INT("&color not defined", __func__, 1);
+*pcolor = 0;
+if (!pixs)
+return ERROR_INT("pixs not defined", __func__, 1);
+if ((cmap = pixGetColormap(pixs)) == NULL)
+return 0;
+pixcmapHasColor(cmap, pcolor);
+if (*pcolor == 0)  /* no color */
+return 0;
+/* The cmap has color entries.  Are they used? */
+na = pixGetGrayHistogram(pixs, 1);
+n = pixcmapGetCount(cmap);
+for (i = 0; i < n; i++) {
+pixcmapGetColor(cmap, i, &rval, &gval, &bval);
+numaGetIValue(na, i, &numpix);
+if ((rval != gval || rval != bval) && numpix) {  /* color found! */
+*pcolor = 1;
+break;
+}
+}
+numaDestroy(&na);
+return 0;
+}
+/*------------------------------------------------------------------*
+*                          Binary correlation                      *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixCorrelationBinary()
+*
+* \param[in]    pix1    1 bpp
+* \param[in]    pix2    1 bpp
+* \param[out]   pval    correlation
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) The correlation is a number between 0.0 and 1.0,
+*          based on foreground similarity:
+*                           (|1 AND 2|)**2
+*            correlation =  --------------
+*                             |1| * |2|
+*          where |x| is the count of foreground pixels in image x.
+*          If the images are identical, this is 1.0.
+*          If they have no fg pixels in common, this is 0.0.
+*          If one or both images have no fg pixels, the correlation is 0.0.
+*      (2) Typically the two images are of equal size, but this
+*          is not enforced.  Instead, the UL corners are aligned.
+* </pre>
+*/
+l_ok
+pixCorrelationBinary(PIX        *pix1,
+PIX        *pix2,
+l_float32  *pval)
+{
+l_int32   count1, count2, countn;
+l_int32  *tab8;
+PIX      *pixn;
+if (!pval)
+return ERROR_INT("&pval not defined", __func__, 1);
+*pval = 0.0;
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+tab8 = makePixelSumTab8();
+pixCountPixels(pix1, &count1, tab8);
+pixCountPixels(pix2, &count2, tab8);
+if (count1 == 0 || count2 == 0) {
+LEPT_FREE(tab8);
+return 0;
+}
+pixn = pixAnd(NULL, pix1, pix2);
+pixCountPixels(pixn, &countn, tab8);
+*pval = (l_float32)countn * (l_float32)countn /
+((l_float32)count1 * (l_float32)count2);
+LEPT_FREE(tab8);
+pixDestroy(&pixn);
+return 0;
+}
+/*------------------------------------------------------------------*
+*                   Difference of two images                       *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixDisplayDiff()
+*
+* \param[in]    pix1       any depth
+* \param[in]    pix2       any depth
+* \param[in]    showall    1 to display input images; 0 to only display result
+* \param[in]    mindiff    min difference to identify pixel
+* \param[in]    diffcolor  color of pixel indicating difference >= mindiff
+* \return  pixd  32 bpp rgb, or NULL on error
+*
+* <pre>
+* Notes:
+*      (1) This aligns the UL corners of pix1 and pix2, crops to the
+*          overlapping pixels, and shows which pixels have a significant
+*          difference in value.
+*      (2) Requires %pix1 and %pix2 to have the same depth.
+*      (3) If rgb, a pixel is identified as different if any component
+*          values of the corresponding pixels equals or exceeds %mindiff.
+*      (4) %diffcolor is in format 0xrrggbbaa.
+*      (5) If %pix1 and %pix2 are 1 bpp, ignores %mindiff and %diffcolor,
+*          and uses the result of pixDisplayDiffBinary().
+* </pre>
+*/
+PIX *
+pixDisplayDiff(PIX      *pix1,
+PIX      *pix2,
+l_int32   showall,
+l_int32   mindiff,
+l_uint32  diffcolor)
+{
+l_int32    i, j, w1, h1, d1, w2, h2, d2, minw, minh, wpl1, wpl2, wpl3;
+l_int32    rval1, gval1, bval1, rval2, gval2, bval2;
+l_uint32   val1, val2;
+l_uint32  *data1, *data2, *data3, *line1, *line2, *line3;
+PIX       *pix3 = NULL, *pix4 = NULL, *pixd;
+PIXA      *pixa1;
+if (!pix1 || !pix2)
+return (PIX *)ERROR_PTR("pix1, pix2 not both defined", __func__, NULL);
+pixGetDimensions(pix1, &w1, &h1, &d1);
+pixGetDimensions(pix2, &w2, &h2, &d2);
+if (d1 != d2)
+return (PIX *)ERROR_PTR("unequal depths", __func__, NULL);
+if (mindiff <= 0)
+return (PIX *)ERROR_PTR("mindiff must be > 0", __func__, NULL);
+if (d1 == 1) {
+pix3 = pixDisplayDiffBinary(pix1, pix2);
+pixd = pixConvertTo32(pix3);
+pixDestroy(&pix3);
+} else {
+minw = L_MIN(w1, w2);
+minh = L_MIN(h1, h2);
+pix3 = pixConvertTo32(pix1);
+pix4 = pixConvertTo32(pix2);
+pixd = pixCreate(minw, minh, 32);
+pixRasterop(pixd, 0, 0, minw, minh, PIX_SRC, pix3, 0, 0);
+data1 = pixGetData(pix3);
+wpl1 = pixGetWpl(pix3);
+data2 = pixGetData(pix4);
+wpl2 = pixGetWpl(pix4);
+data3 = pixGetData(pixd);
+wpl3 = pixGetWpl(pixd);
+for (i = 0; i < minh; i++) {
+line1 = data1 + i * wpl1;
+line2 = data2 + i * wpl2;
+line3 = data3 + i * wpl3;
+for (j = 0; j < minw; j++) {
+val1 = GET_DATA_FOUR_BYTES(line1, j);
+val2 = GET_DATA_FOUR_BYTES(line2, j);
+extractRGBValues(val1, &rval1, &gval1, &bval1);
+extractRGBValues(val2, &rval2, &gval2, &bval2);
+if (L_ABS(rval1 - rval2) >= mindiff ||
+L_ABS(gval1 - gval2) >= mindiff ||
+L_ABS(bval1 - bval2) >= mindiff)
+SET_DATA_FOUR_BYTES(line3, j, diffcolor);
+}
+}
+}
+if (showall) {
+pixa1 = pixaCreate(3);
+if (d1 == 1) {
+pixaAddPix(pixa1, pix1, L_COPY);
+pixaAddPix(pixa1, pix2, L_COPY);
+} else {
+pixaAddPix(pixa1, pix3, L_INSERT);
+pixaAddPix(pixa1, pix4, L_INSERT);
+}
+pixaAddPix(pixa1, pixd, L_INSERT);  /* save diff image */
+pixd = pixaDisplayTiledInColumns(pixa1, 2, 1.0, 30, 2);  /* all 3 */
+pixaDestroy(&pixa1);
+} else if (d1 != 1) {
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+}
+return pixd;
+}
+/*!
+* \brief   pixDisplayDiffBinary()
+*
+* \param[in]    pix1    1 bpp
+* \param[in]    pix2    1 bpp
+* \return  pixd 4 bpp cmapped, or NULL on error
+*
+* <pre>
+* Notes:
+*      (1) This gives a color representation of the difference between
+*          pix1 and pix2.  The color difference depends on the order.
+*          The pixels in pixd have 4 colors:
+*           * unchanged:  black (on), white (off)
+*           * on in pix1, off in pix2: red
+*           * on in pix2, off in pix1: green
+*      (2) This aligns the UL corners of pix1 and pix2, and crops
+*          to the overlapping pixels.
+* </pre>
+*/
+PIX *
+pixDisplayDiffBinary(PIX  *pix1,
+PIX  *pix2)
+{
+l_int32   w1, h1, d1, w2, h2, d2, minw, minh;
+PIX      *pixt, *pixd;
+PIXCMAP  *cmap;
+if (!pix1 || !pix2)
+return (PIX *)ERROR_PTR("pix1, pix2 not both defined", __func__, NULL);
+pixGetDimensions(pix1, &w1, &h1, &d1);
+pixGetDimensions(pix2, &w2, &h2, &d2);
+if (d1 != 1 || d2 != 1)
+return (PIX *)ERROR_PTR("pix1 and pix2 not 1 bpp", __func__, NULL);
+minw = L_MIN(w1, w2);
+minh = L_MIN(h1, h2);
+pixd = pixCreate(minw, minh, 4);
+cmap = pixcmapCreate(4);
+pixcmapAddColor(cmap, 255, 255, 255);  /* initialized to white */
+pixcmapAddColor(cmap, 0, 0, 0);
+pixcmapAddColor(cmap, 255, 0, 0);
+pixcmapAddColor(cmap, 0, 255, 0);
+pixSetColormap(pixd, cmap);
+pixt = pixAnd(NULL, pix1, pix2);
+pixPaintThroughMask(pixd, pixt, 0, 0, 0x0);  /* black */
+pixSubtract(pixt, pix1, pix2);
+pixPaintThroughMask(pixd, pixt, 0, 0, 0xff000000);  /* red */
+pixSubtract(pixt, pix2, pix1);
+pixPaintThroughMask(pixd, pixt, 0, 0, 0x00ff0000);  /* green */
+pixDestroy(&pixt);
+return pixd;
+}
+/*!
+* \brief   pixCompareBinary()
+*
+* \param[in]    pix1       1 bpp
+* \param[in]    pix2       1 bpp
+* \param[in]    comptype   L_COMPARE_XOR, L_COMPARE_SUBTRACT
+* \param[out]   pfract     fraction of pixels that are different
+* \param[out]   ppixdiff   [optional] pix of difference
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) The two images are aligned at the UL corner, and do not
+*          need to be the same size.
+*      (2) If using L_COMPARE_SUBTRACT, pix2 is subtracted from pix1.
+*      (3) The total number of pixels is determined by pix1.
+*      (4) On error, the returned fraction is 1.0.
+* </pre>
+*/
+l_ok
+pixCompareBinary(PIX        *pix1,
+PIX        *pix2,
+l_int32     comptype,
+l_float32  *pfract,
+PIX       **ppixdiff)
+{
+l_int32   w, h, count;
+PIX      *pixt;
+if (ppixdiff) *ppixdiff = NULL;
+if (!pfract)
+return ERROR_INT("&pfract not defined", __func__, 1);
+*pfract = 1.0;  /* initialize to max difference */
+if (!pix1 || pixGetDepth(pix1) != 1)
+return ERROR_INT("pix1 not defined or not 1 bpp", __func__, 1);
+if (!pix2 || pixGetDepth(pix2) != 1)
+return ERROR_INT("pix2 not defined or not 1 bpp", __func__, 1);
+if (comptype != L_COMPARE_XOR && comptype != L_COMPARE_SUBTRACT)
+return ERROR_INT("invalid comptype", __func__, 1);
+if (comptype == L_COMPARE_XOR)
+pixt = pixXor(NULL, pix1, pix2);
+else  /* comptype == L_COMPARE_SUBTRACT) */
+pixt = pixSubtract(NULL, pix1, pix2);
+pixCountPixels(pixt, &count, NULL);
+pixGetDimensions(pix1, &w, &h, NULL);
+*pfract = (l_float32)(count) / (l_float32)(w * h);
+if (ppixdiff)
+*ppixdiff = pixt;
+else
+pixDestroy(&pixt);
+return 0;
+}
+/*!
+* \brief   pixCompareGrayOrRGB()
+*
+* \param[in]    pix1      2,4,8,16 bpp gray, 32 bpp rgb, or colormapped
+* \param[in]    pix2      2,4,8,16 bpp gray, 32 bpp rgb, or colormapped
+* \param[in]    comptype  L_COMPARE_SUBTRACT, L_COMPARE_ABS_DIFF
+* \param[in]    plottype  gplot plot output type, or 0 for no plot
+* \param[out]   psame     [optional] 1 if pixel values are identical
+* \param[out]   pdiff     [optional] average difference
+* \param[out]   prmsdiff  [optional] rms of difference
+* \param[out]   ppixdiff  [optional] pix of difference
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) The two images are aligned at the UL corner, and do not
+*          need to be the same size.  If they are not the same size,
+*          the comparison will be made over overlapping pixels.
+*      (2) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (3) If RGB, each component is compared separately.
+*      (4) If type is L_COMPARE_ABS_DIFF, pix2 is subtracted from pix1
+*          and the absolute value is taken.
+*      (5) If type is L_COMPARE_SUBTRACT, pix2 is subtracted from pix1
+*          and the result is clipped to 0.
+*      (6) The plot output types are specified in gplot.h.
+*          Use 0 if no difference plot is to be made.
+*      (7) If the images are pixelwise identical, no difference
+*          plot is made, even if requested.  The result (TRUE or FALSE)
+*          is optionally returned in the parameter 'same'.
+*      (8) The average difference (either subtracting or absolute value)
+*          is optionally returned in the parameter 'diff'.
+*      (9) The RMS difference is optionally returned in the
+*          parameter 'rmsdiff'.  For RGB, we return the average of
+*          the RMS differences for each of the components.
+*     (10) Because pixel values are compared, pix1 and pix2 can be equal when:
+*          * they are both gray with different depth
+*          * one is colormapped and the other is not
+*          * they are both colormapped and have different size colormaps
+* </pre>
+*/
+l_ok
+pixCompareGrayOrRGB(PIX        *pix1,
+PIX        *pix2,
+l_int32     comptype,
+l_int32     plottype,
+l_int32    *psame,
+l_float32  *pdiff,
+l_float32  *prmsdiff,
+PIX       **ppixdiff)
+{
+l_int32  retval, d1, d2;
+PIX     *pixt1, *pixt2, *pixs1, *pixs2;
+if (psame) *psame = 0;
+if (pdiff) *pdiff = 255.0;
+if (prmsdiff) *prmsdiff = 255.0;
+if (ppixdiff) *ppixdiff = NULL;
+if (!pix1 || pixGetDepth(pix1) == 1)
+return ERROR_INT("pix1 not defined or 1 bpp", __func__, 1);
+if (!pix2 || pixGetDepth(pix2) == 1)
+return ERROR_INT("pix2 not defined or 1 bpp", __func__, 1);
+if (comptype != L_COMPARE_SUBTRACT && comptype != L_COMPARE_ABS_DIFF)
+return ERROR_INT("invalid comptype", __func__, 1);
+if (plottype < 0 || plottype >= NUM_GPLOT_OUTPUTS)
+return ERROR_INT("invalid plottype", __func__, 1);
+pixt1 = pixRemoveColormap(pix1, REMOVE_CMAP_BASED_ON_SRC);
+pixt2 = pixRemoveColormap(pix2, REMOVE_CMAP_BASED_ON_SRC);
+d1 = pixGetDepth(pixt1);
+d2 = pixGetDepth(pixt2);
+if (d1 < 8)
+pixs1 = pixConvertTo8(pixt1, FALSE);
+else
+pixs1 = pixClone(pixt1);
+if (d2 < 8)
+pixs2 = pixConvertTo8(pixt2, FALSE);
+else
+pixs2 = pixClone(pixt2);
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+d1 = pixGetDepth(pixs1);
+d2 = pixGetDepth(pixs2);
+if (d1 != d2) {
+pixDestroy(&pixs1);
+pixDestroy(&pixs2);
+return ERROR_INT("intrinsic depths are not equal", __func__, 1);
+}
+if (d1 == 8 || d1 == 16)
+retval = pixCompareGray(pixs1, pixs2, comptype, plottype, psame,
+pdiff, prmsdiff, ppixdiff);
+else  /* d1 == 32 */
+retval = pixCompareRGB(pixs1, pixs2, comptype, plottype, psame,
+pdiff, prmsdiff, ppixdiff);
+pixDestroy(&pixs1);
+pixDestroy(&pixs2);
+return retval;
+}
+/*!
+* \brief   pixCompareGray()
+*
+* \param[in]    pix1       8 or 16 bpp, not cmapped
+* \param[in]    pix2       8 or 16 bpp, not cmapped
+* \param[in]    comptype   L_COMPARE_SUBTRACT, L_COMPARE_ABS_DIFF
+* \param[in]    plottype   gplot plot output type, or 0 for no plot
+* \param[out]   psame      [optional] 1 if pixel values are identical
+* \param[out]   pdiff      [optional] average difference
+* \param[out]   prmsdiff   [optional] rms of difference
+* \param[out]   ppixdiff   [optional] pix of difference
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) See pixCompareGrayOrRGB() for details.
+*      (2) Use pixCompareGrayOrRGB() if the input pix are colormapped.
+*      (3) Note: setting %plottype > 0 can result in writing named
+*                output files.
+* </pre>
+*/
+l_ok
+pixCompareGray(PIX        *pix1,
+PIX        *pix2,
+l_int32     comptype,
+l_int32     plottype,
+l_int32    *psame,
+l_float32  *pdiff,
+l_float32  *prmsdiff,
+PIX       **ppixdiff)
+{
+char            buf[64];
+static l_atomic index = 0;
+l_int32         d1, d2, same, first, last;
+GPLOT          *gplot;
+NUMA           *na, *nac;
+PIX            *pixt;
+if (psame) *psame = 0;
+if (pdiff) *pdiff = 255.0;
+if (prmsdiff) *prmsdiff = 255.0;
+if (ppixdiff) *ppixdiff = NULL;
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+d1 = pixGetDepth(pix1);
+d2 = pixGetDepth(pix2);
+if ((d1 != d2) || (d1 != 8 && d1 != 16))
+return ERROR_INT("depths unequal or not 8 or 16 bpp", __func__, 1);
+if (pixGetColormap(pix1) || pixGetColormap(pix2))
+return ERROR_INT("pix1 and/or pix2 are colormapped", __func__, 1);
+if (comptype != L_COMPARE_SUBTRACT && comptype != L_COMPARE_ABS_DIFF)
+return ERROR_INT("invalid comptype", __func__, 1);
+if (plottype < 0 || plottype >= NUM_GPLOT_OUTPUTS)
+return ERROR_INT("invalid plottype", __func__, 1);
+lept_mkdir("lept/comp");
+if (comptype == L_COMPARE_SUBTRACT)
+pixt = pixSubtractGray(NULL, pix1, pix2);
+else  /* comptype == L_COMPARE_ABS_DIFF) */
+pixt = pixAbsDifference(pix1, pix2);
+pixZero(pixt, &same);
+if (same)
+L_INFO("Images are pixel-wise identical\n", __func__);
+if (psame) *psame = same;
+if (pdiff)
+pixGetAverageMasked(pixt, NULL, 0, 0, 1, L_MEAN_ABSVAL, pdiff);
+/* Don't bother to plot if the images are the same */
+if (plottype && !same) {
+L_INFO("Images differ: output plots will be generated\n", __func__);
+na = pixGetGrayHistogram(pixt, 1);
+numaGetNonzeroRange(na, TINY, &first, &last);
+nac = numaClipToInterval(na, 0, last);
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/compare_gray%d", index);
+gplot = gplotCreate(buf, plottype,
+"Pixel Difference Histogram", "diff val",
+"number of pixels");
+gplotAddPlot(gplot, NULL, nac, GPLOT_LINES, "gray");
+gplotMakeOutput(gplot);
+gplotDestroy(&gplot);
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/compare_gray%d.png",
+index++);
+l_fileDisplay(buf, 100, 100, 1.0);
+numaDestroy(&na);
+numaDestroy(&nac);
+}
+if (ppixdiff)
+*ppixdiff = pixCopy(NULL, pixt);
+if (prmsdiff) {
+if (comptype == L_COMPARE_SUBTRACT) {  /* wrong type for rms diff */
+pixDestroy(&pixt);
+pixt = pixAbsDifference(pix1, pix2);
+}
+pixGetAverageMasked(pixt, NULL, 0, 0, 1, L_ROOT_MEAN_SQUARE, prmsdiff);
+}
+pixDestroy(&pixt);
+return 0;
+}
+/*!
+* \brief   pixCompareRGB()
+*
+* \param[in]    pix1       32 bpp rgb
+* \param[in]    pix2       32 bpp rgb
+* \param[in]    comptype   L_COMPARE_SUBTRACT, L_COMPARE_ABS_DIFF
+* \param[in]    plottype   gplot plot output type, or 0 for no plot
+* \param[out]   psame      [optional] 1 if pixel values are identical
+* \param[out]   pdiff      [optional] average difference
+* \param[out]   prmsdiff   [optional] rms of difference
+* \param[out]   ppixdiff   [optional] pix of difference
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) See pixCompareGrayOrRGB() for details.
+*      (2) Note: setting %plottype > 0 can result in writing named
+*                output files.
+* </pre>
+*/
+l_ok
+pixCompareRGB(PIX        *pix1,
+PIX        *pix2,
+l_int32     comptype,
+l_int32     plottype,
+l_int32    *psame,
+l_float32  *pdiff,
+l_float32  *prmsdiff,
+PIX       **ppixdiff)
+{
+char            buf[64];
+static l_atomic index = 0;
+l_int32         rsame, gsame, bsame, same, first, rlast, glast, blast, last;
+l_float32       rdiff, gdiff, bdiff;
+GPLOT          *gplot;
+NUMA           *nar, *nag, *nab, *narc, *nagc, *nabc;
+PIX            *pixr1, *pixr2, *pixg1, *pixg2, *pixb1, *pixb2;
+PIX            *pixr, *pixg, *pixb;
+if (psame) *psame = 0;
+if (pdiff) *pdiff = 0.0;
+if (prmsdiff) *prmsdiff = 0.0;
+if (ppixdiff) *ppixdiff = NULL;
+if (!pix1 || pixGetDepth(pix1) != 32)
+return ERROR_INT("pix1 not defined or not 32 bpp", __func__, 1);
+if (!pix2 || pixGetDepth(pix2) != 32)
+return ERROR_INT("pix2 not defined or not ew bpp", __func__, 1);
+if (comptype != L_COMPARE_SUBTRACT && comptype != L_COMPARE_ABS_DIFF)
+return ERROR_INT("invalid comptype", __func__, 1);
+if (plottype < 0 || plottype >= NUM_GPLOT_OUTPUTS)
+return ERROR_INT("invalid plottype", __func__, 1);
+lept_mkdir("lept/comp");
+pixr1 = pixGetRGBComponent(pix1, COLOR_RED);
+pixr2 = pixGetRGBComponent(pix2, COLOR_RED);
+pixg1 = pixGetRGBComponent(pix1, COLOR_GREEN);
+pixg2 = pixGetRGBComponent(pix2, COLOR_GREEN);
+pixb1 = pixGetRGBComponent(pix1, COLOR_BLUE);
+pixb2 = pixGetRGBComponent(pix2, COLOR_BLUE);
+if (comptype == L_COMPARE_SUBTRACT) {
+pixr = pixSubtractGray(NULL, pixr1, pixr2);
+pixg = pixSubtractGray(NULL, pixg1, pixg2);
+pixb = pixSubtractGray(NULL, pixb1, pixb2);
+} else { /* comptype == L_COMPARE_ABS_DIFF) */
+pixr = pixAbsDifference(pixr1, pixr2);
+pixg = pixAbsDifference(pixg1, pixg2);
+pixb = pixAbsDifference(pixb1, pixb2);
+}
+pixZero(pixr, &rsame);
+pixZero(pixg, &gsame);
+pixZero(pixb, &bsame);
+same = rsame && gsame && bsame;
+if (same)
+L_INFO("Images are pixel-wise identical\n", __func__);
+if (psame) *psame = same;
+if (pdiff) {
+pixGetAverageMasked(pixr, NULL, 0, 0, 1, L_MEAN_ABSVAL, &rdiff);
+pixGetAverageMasked(pixg, NULL, 0, 0, 1, L_MEAN_ABSVAL, &gdiff);
+pixGetAverageMasked(pixb, NULL, 0, 0, 1, L_MEAN_ABSVAL, &bdiff);
+*pdiff = (rdiff + gdiff + bdiff) / 3.0;
+}
+/* Don't bother to plot if the images are the same */
+if (plottype && !same) {
+L_INFO("Images differ: output plots will be generated\n", __func__);
+nar = pixGetGrayHistogram(pixr, 1);
+nag = pixGetGrayHistogram(pixg, 1);
+nab = pixGetGrayHistogram(pixb, 1);
+numaGetNonzeroRange(nar, TINY, &first, &rlast);
+numaGetNonzeroRange(nag, TINY, &first, &glast);
+numaGetNonzeroRange(nab, TINY, &first, &blast);
+last = L_MAX(rlast, glast);
+last = L_MAX(last, blast);
+narc = numaClipToInterval(nar, 0, last);
+nagc = numaClipToInterval(nag, 0, last);
+nabc = numaClipToInterval(nab, 0, last);
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/compare_rgb%d", index);
+gplot = gplotCreate(buf, plottype,
+"Pixel Difference Histogram", "diff val",
+"number of pixels");
+gplotAddPlot(gplot, NULL, narc, GPLOT_LINES, "red");
+gplotAddPlot(gplot, NULL, nagc, GPLOT_LINES, "green");
+gplotAddPlot(gplot, NULL, nabc, GPLOT_LINES, "blue");
+gplotMakeOutput(gplot);
+gplotDestroy(&gplot);
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/compare_rgb%d.png",
+index++);
+l_fileDisplay(buf, 100, 100, 1.0);
+numaDestroy(&nar);
+numaDestroy(&nag);
+numaDestroy(&nab);
+numaDestroy(&narc);
+numaDestroy(&nagc);
+numaDestroy(&nabc);
+}
+if (ppixdiff)
+*ppixdiff = pixCreateRGBImage(pixr, pixg, pixb);
+if (prmsdiff) {
+if (comptype == L_COMPARE_SUBTRACT) {
+pixDestroy(&pixr);
+pixDestroy(&pixg);
+pixDestroy(&pixb);
+pixr = pixAbsDifference(pixr1, pixr2);
+pixg = pixAbsDifference(pixg1, pixg2);
+pixb = pixAbsDifference(pixb1, pixb2);
+}
+pixGetAverageMasked(pixr, NULL, 0, 0, 1, L_ROOT_MEAN_SQUARE, &rdiff);
+pixGetAverageMasked(pixg, NULL, 0, 0, 1, L_ROOT_MEAN_SQUARE, &gdiff);
+pixGetAverageMasked(pixb, NULL, 0, 0, 1, L_ROOT_MEAN_SQUARE, &bdiff);
+*prmsdiff = (rdiff + gdiff + bdiff) / 3.0;
+}
+pixDestroy(&pixr1);
+pixDestroy(&pixr2);
+pixDestroy(&pixg1);
+pixDestroy(&pixg2);
+pixDestroy(&pixb1);
+pixDestroy(&pixb2);
+pixDestroy(&pixr);
+pixDestroy(&pixg);
+pixDestroy(&pixb);
+return 0;
+}
+/*!
+* \brief   pixCompareTiled()
+*
+* \param[in]    pix1       8 bpp or 32 bpp rgb
+* \param[in]    pix2       8 bpp 32 bpp rgb
+* \param[in]    sx, sy     tile size; must be > 1 in each dimension
+* \param[in]    type       L_MEAN_ABSVAL or L_ROOT_MEAN_SQUARE
+* \param[out]   ppixdiff   pix of difference
+* \return  0 if OK; 1 on error
+*
+* <pre>
+* Notes:
+*      (1) With L_MEAN_ABSVAL, we compute for each tile the
+*          average abs value of the pixel component difference between
+*          the two (aligned) images.  With L_ROOT_MEAN_SQUARE, we
+*          compute instead the rms difference over all components.
+*      (2) The two input pix must be the same depth.  Comparison is made
+*          using UL corner alignment.
+*      (3) For 32 bpp, the distance between corresponding tiles
+*          is found by averaging the measured difference over all three
+*          components of each pixel in the tile.
+*      (4) The result, pixdiff, contains one pixel for each source tile.
+* </pre>
+*/
+l_ok
+pixCompareTiled(PIX     *pix1,
+PIX     *pix2,
+l_int32  sx,
+l_int32  sy,
+l_int32  type,
+PIX    **ppixdiff)
+{
+l_int32    d1, d2, w, h;
+PIX       *pixt, *pixr, *pixg, *pixb;
+PIX       *pixrdiff, *pixgdiff, *pixbdiff;
+PIXACC    *pixacc;
+if (!ppixdiff)
+return ERROR_INT("&pixdiff not defined", __func__, 1);
+*ppixdiff = NULL;
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+d1 = pixGetDepth(pix1);
+d2 = pixGetDepth(pix2);
+if (d1 != d2)
+return ERROR_INT("depths not equal", __func__, 1);
+if (d1 != 8 && d1 != 32)
+return ERROR_INT("pix1 not 8 or 32 bpp", __func__, 1);
+if (d2 != 8 && d2 != 32)
+return ERROR_INT("pix2 not 8 or 32 bpp", __func__, 1);
+if (sx < 2 || sy < 2)
+return ERROR_INT("sx and sy not both > 1", __func__, 1);
+if (type != L_MEAN_ABSVAL && type != L_ROOT_MEAN_SQUARE)
+return ERROR_INT("invalid type", __func__, 1);
+pixt = pixAbsDifference(pix1, pix2);
+if (d1 == 8) {
+*ppixdiff = pixGetAverageTiled(pixt, sx, sy, type);
+} else {  /* d1 == 32 */
+pixr = pixGetRGBComponent(pixt, COLOR_RED);
+pixg = pixGetRGBComponent(pixt, COLOR_GREEN);
+pixb = pixGetRGBComponent(pixt, COLOR_BLUE);
+pixrdiff = pixGetAverageTiled(pixr, sx, sy, type);
+pixgdiff = pixGetAverageTiled(pixg, sx, sy, type);
+pixbdiff = pixGetAverageTiled(pixb, sx, sy, type);
+pixGetDimensions(pixrdiff, &w, &h, NULL);
+pixacc = pixaccCreate(w, h, 0);
+pixaccAdd(pixacc, pixrdiff);
+pixaccAdd(pixacc, pixgdiff);
+pixaccAdd(pixacc, pixbdiff);
+pixaccMultConst(pixacc, 1.f / 3.f);
+*ppixdiff = pixaccFinal(pixacc, 8);
+pixDestroy(&pixr);
+pixDestroy(&pixg);
+pixDestroy(&pixb);
+pixDestroy(&pixrdiff);
+pixDestroy(&pixgdiff);
+pixDestroy(&pixbdiff);
+pixaccDestroy(&pixacc);
+}
+pixDestroy(&pixt);
+return 0;
+}
+/*------------------------------------------------------------------*
+*            Other measures of the difference of two images        *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixCompareRankDifference()
+*
+* \param[in]    pix1      8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    pix2      8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    factor    subsampling factor; use 0 or 1 for no subsampling
+* \return  narank      numa of rank difference, or NULL on error
+*
+* <pre>
+* Notes:
+*      (1) This answers the question: if the pixel values in each
+*          component are compared by absolute difference, for
+*          any value of difference, what is the fraction of
+*          pixel pairs that have a difference of this magnitude
+*          or greater.  For a difference of 0, the fraction is 1.0.
+*          In this sense, it is a mapping from pixel difference to
+*          rank order of difference.
+*      (2) The two images are aligned at the UL corner, and do not
+*          need to be the same size.  If they are not the same size,
+*          the comparison will be made over overlapping pixels.
+*      (3) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (4) If RGB, pixel differences for each component are aggregated
+*          into a single histogram.
+* </pre>
+*/
+NUMA *
+pixCompareRankDifference(PIX     *pix1,
+PIX     *pix2,
+l_int32  factor)
+{
+l_int32     i;
+l_float32  *array1, *array2;
+NUMA       *nah, *nan, *nad;
+if (!pix1)
+return (NUMA *)ERROR_PTR("pix1 not defined", __func__, NULL);
+if (!pix2)
+return (NUMA *)ERROR_PTR("pix2 not defined", __func__, NULL);
+if ((nah = pixGetDifferenceHistogram(pix1, pix2, factor)) == NULL)
+return (NUMA *)ERROR_PTR("na not made", __func__, NULL);
+nan = numaNormalizeHistogram(nah, 1.0);
+array1 = numaGetFArray(nan, L_NOCOPY);
+nad = numaCreate(256);
+numaSetCount(nad, 256);  /* all initialized to 0.0 */
+array2 = numaGetFArray(nad, L_NOCOPY);
+/* Do rank accumulation on normalized histo of diffs */
+array2[0] = 1.0;
+for (i = 1; i < 256; i++)
+array2[i] = array2[i - 1] - array1[i - 1];
+numaDestroy(&nah);
+numaDestroy(&nan);
+return nad;
+}
+/*!
+* \brief   pixTestForSimilarity()
+*
+* \param[in]    pix1         8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    pix2         8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    factor       subsampling factor; use 0 or 1 for no subsampling
+* \param[in]    mindiff      minimum pixel difference to be counted; > 0
+* \param[in]    maxfract     maximum fraction of pixels allowed to have
+*                            diff greater than or equal to mindiff
+* \param[in]    maxave       maximum average difference of pixels allowed for
+*                            pixels with diff greater than or equal to
+*                            mindiff, after subtracting mindiff
+* \param[out]   psimilar     1 if similar, 0 otherwise
+* \param[in]    details      use 1 to give normalized histogram and other data
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This takes 2 pix that are the same size and determines using
+*          3 input parameters if they are "similar".  The first parameter
+*          %mindiff establishes a criterion of pixel-to-pixel similarity:
+*          two pixels are not similar if their difference in value is
+*          at least mindiff.  Then %maxfract and %maxave are thresholds
+*          on the number and distribution of dissimilar pixels
+*          allowed for the two pix to be similar.   If the pix are
+*          to be similar, neither threshold can be exceeded.
+*      (2) In setting the %maxfract and %maxave thresholds, you have
+*          these options:
+*            (a) Base the comparison only on %maxfract.  Then set
+*                %maxave = 0.0 or 256.0.  (If 0, we always ignore it.)
+*            (b) Base the comparison only on %maxave.  Then set
+*                %maxfract = 1.0.
+*            (c) Base the comparison on both thresholds.
+*      (3) Example of values that can be expected at mindiff = 15 when
+*          comparing lossless png encoding with jpeg encoding, q=75:
+*             (smoothish bg)       fractdiff = 0.01, avediff = 2.5
+*             (natural scene)      fractdiff = 0.13, avediff = 3.5
+*          To identify these images as 'similar', select maxfract
+*          and maxave to be upper bounds of what you expect.
+*      (4) See pixGetDifferenceStats() for a discussion of why we subtract
+*          mindiff from the computed average diff of the nonsimilar pixels
+*          to get the 'avediff' returned by that function.
+*      (5) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (6) If RGB, the maximum difference between pixel components is
+*          saved in the histogram.
+* </pre>
+*/
+l_ok
+pixTestForSimilarity(PIX       *pix1,
+PIX       *pix2,
+l_int32    factor,
+l_int32    mindiff,
+l_float32  maxfract,
+l_float32  maxave,
+l_int32   *psimilar,
+l_int32    details)
+{
+l_float32   fractdiff, avediff;
+if (!psimilar)
+return ERROR_INT("&similar not defined", __func__, 1);
+*psimilar = 0;
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+if (pixSizesEqual(pix1, pix2) == 0)
+return ERROR_INT("pix sizes not equal", __func__, 1);
+if (mindiff <= 0)
+return ERROR_INT("mindiff must be > 0", __func__, 1);
+if (pixGetDifferenceStats(pix1, pix2, factor, mindiff,
+&fractdiff, &avediff, details))
+return ERROR_INT("diff stats not found", __func__, 1);
+if (maxave <= 0.0) maxave = 256.0;
+if (fractdiff <= maxfract && avediff <= maxave)
+*psimilar = 1;
+return 0;
+}
+/*!
+* \brief   pixGetDifferenceStats()
+*
+* \param[in]    pix1        8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    pix2        8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    factor      subsampling factor; use 0 or 1 for no subsampling
+* \param[in]    mindiff     minimum pixel difference to be counted; > 0
+* \param[out]   pfractdiff  fraction of pixels with diff greater than or
+*                           equal to mindiff
+* \param[out]   pavediff    average difference of pixels with diff greater
+*                           than or equal to mindiff, less mindiff
+* \param[in]    details     use 1 to give normalized histogram and other data
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This takes a threshold %mindiff and describes the difference
+*          between two images in terms of two numbers:
+*            (a) the fraction of pixels, %fractdiff, whose difference
+*                equals or exceeds the threshold %mindiff, and
+*            (b) the average value %avediff of the difference in pixel value
+*                for the pixels in the set given by (a), after you subtract
+*                %mindiff.  The reason for subtracting %mindiff is that
+*                you then get a useful measure for the rate of falloff
+*                of the distribution for larger differences.  For example,
+*                if %mindiff = 10 and you find that %avediff = 2.5, it
+*                says that of the pixels with diff > 10, the average of
+*                their diffs is just mindiff + 2.5 = 12.5.  This is a
+*                fast falloff in the histogram with increasing difference.
+*      (2) The two images are aligned at the UL corner, and do not
+*          need to be the same size.  If they are not the same size,
+*          the comparison will be made over overlapping pixels.
+*      (3) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (4) If RGB, the maximum difference between pixel components is
+*          saved in the histogram.
+*      (5) Set %details == 1 to see the difference histogram and get
+*          an output that shows for each value of %mindiff, what are the
+*          minimum values required for fractdiff and avediff in order
+*          that the two pix will be considered similar.
+* </pre>
+*/
+l_ok
+pixGetDifferenceStats(PIX        *pix1,
+PIX        *pix2,
+l_int32     factor,
+l_int32     mindiff,
+l_float32  *pfractdiff,
+l_float32  *pavediff,
+l_int32     details)
+{
+l_int32     i, first, last, diff;
+l_float32   fract, ave;
+l_float32  *array;
+NUMA       *nah, *nan, *nac;
+if (pfractdiff) *pfractdiff = 0.0;
+if (pavediff) *pavediff = 0.0;
+if (!pfractdiff)
+return ERROR_INT("&fractdiff not defined", __func__, 1);
+if (!pavediff)
+return ERROR_INT("&avediff not defined", __func__, 1);
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+if (mindiff <= 0)
+return ERROR_INT("mindiff must be > 0", __func__, 1);
+if ((nah = pixGetDifferenceHistogram(pix1, pix2, factor)) == NULL)
+return ERROR_INT("na not made", __func__, 1);
+if ((nan = numaNormalizeHistogram(nah, 1.0)) == NULL) {
+numaDestroy(&nah);
+return ERROR_INT("nan not made", __func__, 1);
+}
+array = numaGetFArray(nan, L_NOCOPY);
+if (details) {
+lept_mkdir("lept/comp");
+numaGetNonzeroRange(nan, 0.0, &first, &last);
+nac = numaClipToInterval(nan, first, last);
+gplotSimple1(nac, GPLOT_PNG, "/tmp/lept/comp/histo",
+"Difference histogram");
+l_fileDisplay("/tmp/lept/comp/histo.png", 500, 0, 1.0);
+lept_stderr("\nNonzero values in normalized histogram:");
+numaWriteStderr(nac);
+numaDestroy(&nac);
+lept_stderr(" Mindiff      fractdiff      avediff\n");
+lept_stderr(" -----------------------------------\n");
+for (diff = 1; diff < L_MIN(2 * mindiff, last); diff++) {
+fract = 0.0;
+ave = 0.0;
+for (i = diff; i <= last; i++) {
+fract += array[i];
+ave += (l_float32)i * array[i];
+}
+ave = (fract == 0.0) ? 0.0 : ave / fract;
+ave -= diff;
+lept_stderr("%5d         %7.4f        %7.4f\n",
+diff, fract, ave);
+}
+lept_stderr(" -----------------------------------\n");
+}
+fract = 0.0;
+ave = 0.0;
+for (i = mindiff; i < 256; i++) {
+fract += array[i];
+ave += (l_float32)i * array[i];
+}
+ave = (fract == 0.0) ? 0.0 : ave / fract;
+ave -= mindiff;
+*pfractdiff = fract;
+*pavediff = ave;
+numaDestroy(&nah);
+numaDestroy(&nan);
+return 0;
+}
+/*!
+* \brief   pixGetDifferenceHistogram()
+*
+* \param[in]    pix1      8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    pix2      8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    factor    subsampling factor; use 0 or 1 for no subsampling
+* \return  na     Numa of histogram of differences, or NULL on error
+*
+* <pre>
+* Notes:
+*      (1) The two images are aligned at the UL corner, and do not
+*          need to be the same size.  If they are not the same size,
+*          the comparison will be made over overlapping pixels.
+*      (2) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (3) If RGB, the maximum difference between pixel components is
+*          saved in the histogram.
+* </pre>
+*/
+NUMA *
+pixGetDifferenceHistogram(PIX     *pix1,
+PIX     *pix2,
+l_int32  factor)
+{
+l_int32     w1, h1, d1, w2, h2, d2, w, h, wpl1, wpl2;
+l_int32     i, j, val, val1, val2;
+l_int32     rval1, rval2, gval1, gval2, bval1, bval2;
+l_int32     rdiff, gdiff, bdiff, maxdiff;
+l_uint32   *data1, *data2, *line1, *line2;
+l_float32  *array;
+NUMA       *na;
+PIX        *pixt1, *pixt2;
+if (!pix1)
+return (NUMA *)ERROR_PTR("pix1 not defined", __func__, NULL);
+if (!pix2)
+return (NUMA *)ERROR_PTR("pix2 not defined", __func__, NULL);
+d1 = pixGetDepth(pix1);
+d2 = pixGetDepth(pix2);
+if (d1 == 16 || d2 == 16)
+return (NUMA *)ERROR_PTR("d == 16 not supported", __func__, NULL);
+if (d1 < 8 && !pixGetColormap(pix1))
+return (NUMA *)ERROR_PTR("pix1 depth < 8 bpp and not cmapped",
+__func__, NULL);
+if (d2 < 8 && !pixGetColormap(pix2))
+return (NUMA *)ERROR_PTR("pix2 depth < 8 bpp and not cmapped",
+__func__, NULL);
+pixt1 = pixRemoveColormap(pix1, REMOVE_CMAP_BASED_ON_SRC);
+pixt2 = pixRemoveColormap(pix2, REMOVE_CMAP_BASED_ON_SRC);
+pixGetDimensions(pixt1, &w1, &h1, &d1);
+pixGetDimensions(pixt2, &w2, &h2, &d2);
+if (d1 != d2) {
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return (NUMA *)ERROR_PTR("pix depths not equal", __func__, NULL);
+}
+if (factor < 1) factor = 1;
+na = numaCreate(256);
+numaSetCount(na, 256);  /* all initialized to 0.0 */
+array = numaGetFArray(na, L_NOCOPY);
+w = L_MIN(w1, w2);
+h = L_MIN(h1, h2);
+data1 = pixGetData(pixt1);
+data2 = pixGetData(pixt2);
+wpl1 = pixGetWpl(pixt1);
+wpl2 = pixGetWpl(pixt2);
+if (d1 == 8) {
+for (i = 0; i < h; i += factor) {
+line1 = data1 + i * wpl1;
+line2 = data2 + i * wpl2;
+for (j = 0; j < w; j += factor) {
+val1 = GET_DATA_BYTE(line1, j);
+val2 = GET_DATA_BYTE(line2, j);
+val = L_ABS(val1 - val2);
+array[val]++;
+}
+}
+} else {  /* d1 == 32 */
+for (i = 0; i < h; i += factor) {
+line1 = data1 + i * wpl1;
+line2 = data2 + i * wpl2;
+for (j = 0; j < w; j += factor) {
+extractRGBValues(line1[j], &rval1, &gval1, &bval1);
+extractRGBValues(line2[j], &rval2, &gval2, &bval2);
+rdiff = L_ABS(rval1 - rval2);
+gdiff = L_ABS(gval1 - gval2);
+bdiff = L_ABS(bval1 - bval2);
+maxdiff = L_MAX(rdiff, gdiff);
+maxdiff = L_MAX(maxdiff, bdiff);
+array[maxdiff]++;
+}
+}
+}
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+return na;
+}
+/*!
+* \brief   pixGetPerceptualDiff()
+*
+* \param[in]    pixs1       8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    pixs2       8 bpp gray or 32 bpp rgb, or colormapped
+* \param[in]    sampling    subsampling factor; use 0 or 1 for no subsampling
+* \param[in]    dilation    size of grayscale or color Sel; odd
+* \param[in]    mindiff     minimum pixel difference to be counted; > 0
+* \param[out]   pfract      fraction of pixels with diff greater than mindiff
+* \param[out]   ppixdiff1   [optional] showing difference (gray or color)
+* \param[out]   ppixdiff2   [optional] showing pixels of sufficient diff
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This takes 2 pix and determines, using 2 input parameters:
+*           * %dilation specifies the amount of grayscale or color
+*             dilation to apply to the images, to compensate for
+*             a small amount of misregistration.  A typical number might
+*             be 5, which uses a 5x5 Sel.  Grayscale dilation expands
+*             lighter pixels into darker pixel regions.
+*           * %mindiff determines the threshold on the difference in
+*             pixel values to be counted -- two pixels are not similar
+*             if their difference in value is at least %mindiff.  For
+*             color pixels, we use the maximum component difference.
+*      (2) The pixelwise comparison is always done with the UL corners
+*          aligned.  The sizes of pix1 and pix2 need not be the same,
+*          although in practice it can be useful to scale to the same size.
+*      (3) If there is a colormap, it is removed and the result
+*          is either gray or RGB depending on the colormap.
+*      (4) Two optional diff images can be retrieved (typ. for debugging):
+*           pixdiff1: the gray or color difference
+*           pixdiff2: thresholded to 1 bpp for pixels exceeding %mindiff
+*      (5) The returned value of fract can be compared to some threshold,
+*          which is application dependent.
+*      (6) This method is in analogy to the two-sided hausdorff transform,
+*          except here it is for d > 1.  For d == 1 (see pixRankHaustest()),
+*          we verify that when one pix1 is dilated, it covers at least a
+*          given fraction of the pixels in pix2, and v.v.; in that
+*          case, the two pix are sufficiently similar.  Here, we
+*          do an analogous thing: subtract the dilated pix1 from pix2 to
+*          get a 1-sided hausdorff-like transform.  Then do it the
+*          other way.  Take the component-wise max of the two results,
+*          and threshold to get the fraction of pixels with a difference
+*          below the threshold.
+* </pre>
+*/
+l_ok
+pixGetPerceptualDiff(PIX        *pixs1,
+PIX        *pixs2,
+l_int32     sampling,
+l_int32     dilation,
+l_int32     mindiff,
+l_float32  *pfract,
+PIX       **ppixdiff1,
+PIX       **ppixdiff2)
+{
+l_int32  d1, d2, w, h, count;
+PIX     *pix1, *pix2, *pix3, *pix4, *pix5, *pix6, *pix7, *pix8, *pix9;
+PIX     *pix10, *pix11;
+if (ppixdiff1) *ppixdiff1 = NULL;
+if (ppixdiff2) *ppixdiff2 = NULL;
+if (!pfract)
+return ERROR_INT("&fract not defined", __func__, 1);
+*pfract = 1.0;  /* init to completely different */
+if ((dilation & 1) == 0)
+return ERROR_INT("dilation must be odd", __func__, 1);
+if (!pixs1)
+return ERROR_INT("pixs1 not defined", __func__, 1);
+if (!pixs2)
+return ERROR_INT("pixs2 not defined", __func__, 1);
+d1 = pixGetDepth(pixs1);
+d2 = pixGetDepth(pixs2);
+if (!pixGetColormap(pixs1) && d1 < 8)
+return ERROR_INT("pixs1 not cmapped and < 8 bpp", __func__, 1);
+if (!pixGetColormap(pixs2) && d2 < 8)
+return ERROR_INT("pixs2 not cmapped and < 8 bpp", __func__, 1);
+/* Integer downsample if requested */
+if (sampling > 1) {
+pix1 = pixScaleByIntSampling(pixs1, sampling);
+pix2 = pixScaleByIntSampling(pixs2, sampling);
+} else {
+pix1 = pixClone(pixs1);
+pix2 = pixClone(pixs2);
+}
+/* Remove colormaps */
+if (pixGetColormap(pix1)) {
+pix3 = pixRemoveColormap(pix1, REMOVE_CMAP_BASED_ON_SRC);
+d1 = pixGetDepth(pix3);
+} else {
+pix3 = pixClone(pix1);
+}
+if (pixGetColormap(pix2)) {
+pix4 = pixRemoveColormap(pix2, REMOVE_CMAP_BASED_ON_SRC);
+d2 = pixGetDepth(pix4);
+} else {
+pix4 = pixClone(pix2);
+}
+pixDestroy(&pix1);
+pixDestroy(&pix2);
+if (d1 != d2 || (d1 != 8 && d1 != 32)) {
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+L_INFO("depths unequal or not in {8,32}: d1 = %d, d2 = %d\n",
+__func__, d1, d2);
+return 1;
+}
+/* In each direction, do a small dilation and subtract the dilated
+* image from the other image to get a one-sided difference.
+* Then take the max of the differences for each direction
+* and clipping each component to 255 if necessary.  Note that
+* for RGB images, the dilations and max selection are done
+* component-wise, and the conversion to grayscale also uses the
+* maximum component.  The resulting grayscale images are
+* thresholded using %mindiff. */
+if (d1 == 8) {
+pix5 = pixDilateGray(pix3, dilation, dilation);
+pixCompareGray(pix4, pix5, L_COMPARE_SUBTRACT, 0, NULL, NULL, NULL,
+&pix7);
+pix6 = pixDilateGray(pix4, dilation, dilation);
+pixCompareGray(pix3, pix6, L_COMPARE_SUBTRACT, 0, NULL, NULL, NULL,
+&pix8);
+pix9 = pixMinOrMax(NULL, pix7, pix8, L_CHOOSE_MAX);
+pix10 = pixThresholdToBinary(pix9, mindiff);
+pixInvert(pix10, pix10);
+pixCountPixels(pix10, &count, NULL);
+pixGetDimensions(pix10, &w, &h, NULL);
+*pfract = (w <= 0 || h <= 0) ? 0.0 :
+(l_float32)count / (l_float32)(w * h);
+pixDestroy(&pix5);
+pixDestroy(&pix6);
+pixDestroy(&pix7);
+pixDestroy(&pix8);
+if (ppixdiff1)
+*ppixdiff1 = pix9;
+else
+pixDestroy(&pix9);
+if (ppixdiff2)
+*ppixdiff2 = pix10;
+else
+pixDestroy(&pix10);
+} else {  /* d1 == 32 */
+pix5 = pixColorMorph(pix3, L_MORPH_DILATE, dilation, dilation);
+pixCompareRGB(pix4, pix5, L_COMPARE_SUBTRACT, 0, NULL, NULL, NULL,
+&pix7);
+pix6 = pixColorMorph(pix4, L_MORPH_DILATE, dilation, dilation);
+pixCompareRGB(pix3, pix6, L_COMPARE_SUBTRACT, 0, NULL, NULL, NULL,
+&pix8);
+pix9 = pixMinOrMax(NULL, pix7, pix8, L_CHOOSE_MAX);
+pix10 = pixConvertRGBToGrayMinMax(pix9, L_CHOOSE_MAX);
+pix11 = pixThresholdToBinary(pix10, mindiff);
+pixInvert(pix11, pix11);
+pixCountPixels(pix11, &count, NULL);
+pixGetDimensions(pix11, &w, &h, NULL);
+*pfract = (w <= 0 || h <= 0) ? 0.0 :
+(l_float32)count / (l_float32)(w * h);
+pixDestroy(&pix5);
+pixDestroy(&pix6);
+pixDestroy(&pix7);
+pixDestroy(&pix8);
+pixDestroy(&pix10);
+if (ppixdiff1)
+*ppixdiff1 = pix9;
+else
+pixDestroy(&pix9);
+if (ppixdiff2)
+*ppixdiff2 = pix11;
+else
+pixDestroy(&pix11);
+}
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+return 0;
+}
+/*!
+* \brief   pixGetPSNR()
+*
+* \param[in]    pix1, pix2     8 or 32 bpp; no colormap
+* \param[in]    factor         sampling factor; >= 1
+* \param[out]   ppsnr          power signal/noise ratio difference
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This computes the power S/N ratio, in dB, for the difference
+*          between two images.  By convention, the power S/N
+*          for a grayscale image is ('log' == log base 10,
+*          and 'ln == log base e):
+*            PSNR = 10 * log((255/MSE)^2)
+*                 = 4.3429 * ln((255/MSE)^2)
+*                 = -4.3429 * ln((MSE/255)^2)
+*          where MSE is the mean squared error.
+*          Here are some examples:
+*             MSE             PSNR
+*             ---             ----
+*             10              28.1
+*             3               38.6
+*             1               48.1
+*             0.1             68.1
+*      (2) If pix1 and pix2 have the same pixel values, the MSE = 0.0
+*          and the PSNR is infinity.  For that case, this returns
+*          PSNR = 1000, which corresponds to the very small MSE of
+*          about 10^(-48).
+* </pre>
+*/
+l_ok
+pixGetPSNR(PIX        *pix1,
+PIX        *pix2,
+l_int32     factor,
+l_float32  *ppsnr)
+{
+l_int32    same, i, j, w, h, d, wpl1, wpl2, v1, v2, r1, g1, b1, r2, g2, b2;
+l_uint32  *data1, *data2, *line1, *line2;
+l_float32  mse;  /* mean squared error */
+if (!ppsnr)
+return ERROR_INT("&psnr not defined", __func__, 1);
+*ppsnr = 0.0;
+if (!pix1 || !pix2)
+return ERROR_INT("empty input pix", __func__, 1);
+if (!pixSizesEqual(pix1, pix2))
+return ERROR_INT("pix sizes unequal", __func__, 1);
+if (pixGetColormap(pix1))
+return ERROR_INT("pix1 has colormap", __func__, 1);
+if (pixGetColormap(pix2))
+return ERROR_INT("pix2 has colormap", __func__, 1);
+pixGetDimensions(pix1, &w, &h, &d);
+if (d != 8 && d != 32)
+return ERROR_INT("pix not 8 or 32 bpp", __func__, 1);
+if (factor < 1)
+return ERROR_INT("invalid sampling factor", __func__, 1);
+pixEqual(pix1, pix2, &same);
+if (same) {
+*ppsnr = 1000.0;  /* crazy big exponent */
+return 0;
+}
+data1 = pixGetData(pix1);
+data2 = pixGetData(pix2);
+wpl1 = pixGetWpl(pix1);
+wpl2 = pixGetWpl(pix2);
+mse = 0.0;
+if (d == 8) {
+for (i = 0; i < h; i += factor) {
+line1 = data1 + i * wpl1;
+line2 = data2 + i * wpl2;
+for (j = 0; j < w; j += factor) {
+v1 = GET_DATA_BYTE(line1, j);
+v2 = GET_DATA_BYTE(line2, j);
+mse += (l_float32)(v1 - v2) * (v1 - v2);
+}
+}
+} else {  /* d == 32 */
+for (i = 0; i < h; i += factor) {
+line1 = data1 + i * wpl1;
+line2 = data2 + i * wpl2;
+for (j = 0; j < w; j += factor) {
+extractRGBValues(line1[j], &r1, &g1, &b1);
+extractRGBValues(line2[j], &r2, &g2, &b2);
+mse += ((l_float32)(r1 - r2) * (r1 - r2) +
+(g1 - g2) * (g1 - g2) +
+(b1 - b2) * (b1 - b2)) / 3.0;
+}
+}
+}
+mse = mse / ((l_float32)(w) * h);
+*ppsnr = -4.3429448 * log(mse / (255 * 255));
+return 0;
+}
+/*------------------------------------------------------------------*
+*             Comparison of photo regions by histogram             *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixaComparePhotoRegionsByHisto()
+*
+* \param[in]    pixa        any depth; colormap OK
+* \param[in]    minratio    requiring sizes be compatible; < 1.0
+* \param[in]    textthresh  threshold for text/photo; use 0 for default
+* \param[in]    factor      subsampling; >= 1
+* \param[in]    n           in range {1, ... 7}. n^2 is the maximum number
+*                           of subregions for histograms; typ. n = 3.
+* \param[in]    simthresh   threshold for similarity; use 0 for default
+* \param[out]   pnai array  giving similarity class indices
+* \param[out]   pscores     [optional] score matrix as 1-D array of size N^2
+* \param[out]   ppixd       [optional] pix of similarity classes
+* \param[in]    debug       1 to output histograms; 0 otherwise
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This function takes a pixa of cropped photo images and
+*          compares each one to the others for similarity.
+*          Each image is first tested to see if it is a photo that can
+*          be compared by tiled histograms.  If so, it is padded to put
+*          the centroid in the center of the image, and the histograms
+*          are generated.  The final step of comparing each histogram
+*          with all the others is very fast.
+*      (2) To make the histograms, each image is subdivided in a maximum
+*          of n^2 subimages.  The parameter %n specifies the "side" of
+*          an n x n grid of such subimages.  If the subimages have an
+*          aspect ratio larger than 2, the grid will change, again using n^2
+*          as a maximum for the number of subimages.  For example,
+*          if n == 3, but the image is 600 x 200 pixels, a 3x3 grid
+*          would have subimages of 200 x 67 pixels, which is more
+*          than 2:1, so we change to a 4x2 grid where each subimage
+*          has 150 x 100 pixels.
+*      (3) An initial filter gives %score = 0 if the ratio of widths
+*          and heights (smallest / largest) does not exceed a
+*          threshold %minratio.  If set at 1.0, both images must be
+*          exactly the same size.  A typical value for %minratio is 0.9.
+*      (4) The comparison score between two images is a value in [0.0 .. 1.0].
+*          If the comparison score >= %simthresh, the images are placed in
+*          the same similarity class.  Default value for %simthresh is 0.25.
+*      (5) An array %nai of similarity class indices for pix in the
+*          input pixa is returned.
+*      (6) There are two debugging options:
+*          * An optional 2D matrix of scores is returned as a 1D array.
+*            A visualization of this is written to a temp file.
+*          * An optional pix showing the similarity classes can be
+*            returned.  Text in each input pix is reproduced.
+*      (7) See the notes in pixComparePhotoRegionsByHisto() for details
+*          on the implementation.
+* </pre>
+*/
+l_ok
+pixaComparePhotoRegionsByHisto(PIXA        *pixa,
+l_float32    minratio,
+l_float32    textthresh,
+l_int32      factor,
+l_int32      n,
+l_float32    simthresh,
+NUMA       **pnai,
+l_float32  **pscores,
+PIX        **ppixd,
+l_int32      debug)
+{
+char       *text;
+l_int32     i, j, nim, w, h, w1, h1, w2, h2, ival, index, classid;
+l_float32   score;
+l_float32  *scores;
+NUMA       *nai, *naw, *nah;
+NUMAA      *naa;
+NUMAA     **n3a;  /* array of naa */
+PIX        *pix;
+if (pscores) *pscores = NULL;
+if (ppixd) *ppixd = NULL;
+if (!pnai)
+return ERROR_INT("&na not defined", __func__, 1);
+*pnai = NULL;
+if (!pixa)
+return ERROR_INT("pixa not defined", __func__, 1);
+if (minratio < 0.0 || minratio > 1.0)
+return ERROR_INT("minratio not in [0.0 ... 1.0]", __func__, 1);
+if (textthresh <= 0.0) textthresh = 1.3f;
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (n < 1 || n > 7) {
+L_WARNING("n = %d is invalid; setting to 4\n", __func__, n);
+n = 4;
+}
+if (simthresh <= 0.0) simthresh = 0.25;
+if (simthresh > 1.0)
+return ERROR_INT("simthresh invalid; should be near 0.25", __func__, 1);
+/* Prepare the histograms */
+nim = pixaGetCount(pixa);
+if ((n3a = (NUMAA **)LEPT_CALLOC(nim, sizeof(NUMAA *))) == NULL)
+return ERROR_INT("calloc fail for n3a", __func__, 1);
+naw = numaCreate(0);
+nah = numaCreate(0);
+for (i = 0; i < nim; i++) {
+pix = pixaGetPix(pixa, i, L_CLONE);
+text = pixGetText(pix);
+pixSetResolution(pix, 150, 150);
+index = (debug) ? i : 0;
+pixGenPhotoHistos(pix, NULL, factor, textthresh, n,
+&naa, &w, &h, index);
+n3a[i] = naa;
+numaAddNumber(naw, w);
+numaAddNumber(nah, h);
+if (naa)
+lept_stderr("Image %s is photo\n", text);
+else
+lept_stderr("Image %s is NOT photo\n", text);
+pixDestroy(&pix);
+}
+/* Do the comparisons.  We are making a set of classes, where
+* all similar images are placed in the same class.  There are
+* 'nim' input images.  The classes are labeled by 'classid' (all
+* similar images get the same 'classid' value), and 'nai' maps
+* the classid of the image in the input array to the classid
+* of the similarity class.  */
+if ((scores =
+(l_float32 *)LEPT_CALLOC((size_t)nim * nim, sizeof(l_float32)))
+== NULL) {
+L_ERROR("calloc fail for scores\n", __func__);
+goto cleanup;
+}
+nai = numaMakeConstant(-1, nim);  /* classid array */
+for (i = 0, classid = 0; i < nim; i++) {
+scores[nim * i + i] = 1.0;
+numaGetIValue(nai, i, &ival);
+if (ival != -1)  /* already set */
+continue;
+numaSetValue(nai, i, classid);
+if (n3a[i] == NULL) {  /* not a photo */
+classid++;
+continue;
+}
+numaGetIValue(naw, i, &w1);
+numaGetIValue(nah, i, &h1);
+for (j = i + 1; j < nim; j++) {
+numaGetIValue(nai, j, &ival);
+if (ival != -1)  /* already set */
+continue;
+if (n3a[j] == NULL)  /* not a photo */
+continue;
+numaGetIValue(naw, j, &w2);
+numaGetIValue(nah, j, &h2);
+compareTilesByHisto(n3a[i], n3a[j], minratio, w1, h1, w2, h2,
+&score, NULL);
+scores[nim * i + j] = score;
+scores[nim * j + i] = score;  /* the score array is symmetric */
+/*            lept_stderr("score = %5.3f\n", score); */
+if (score > simthresh) {
+numaSetValue(nai, j, classid);
+lept_stderr(
+"Setting %d similar to %d, in class %d; score %5.3f\n",
+j, i, classid, score);
+}
+}
+classid++;
+}
+*pnai = nai;
+/* Debug: optionally save and display the score array.
+* All images that are photos are represented by a point on
+* the diagonal. Other images in the same similarity class
+* are on the same horizontal raster line to the right.
+* The array has been symmetrized, so images in the same
+* same similarity class also appear on the same column below. */
+if (pscores) {
+l_int32    wpl, fact;
+l_uint32  *line, *data;
+PIX       *pix2, *pix3;
+pix2 = pixCreate(nim, nim, 8);
+data = pixGetData(pix2);
+wpl = pixGetWpl(pix2);
+for (i = 0; i < nim; i++) {
+line = data + i * wpl;
+for (j = 0; j < nim; j++) {
+SET_DATA_BYTE(line, j,
+L_MIN(255, 4.0 * 255 * scores[nim * i + j]));
+}
+}
+fact = L_MAX(2, 1000 / nim);
+pix3 = pixExpandReplicate(pix2, fact);
+lept_stderr("Writing to /tmp/lept/comp/scorearray.png\n");
+lept_mkdir("lept/comp");
+pixWrite("/tmp/lept/comp/scorearray.png", pix3, IFF_PNG);
+pixDestroy(&pix2);
+pixDestroy(&pix3);
+*pscores = scores;
+} else {
+LEPT_FREE(scores);
+}
+/* Debug: optionally display and save the image comparisons.
+* Image similarity classes are displayed by column; similar
+* images are displayed in the same column. */
+if (ppixd)
+*ppixd = pixaDisplayTiledByIndex(pixa, nai, 200, 20, 2, 6, 0x0000ff00);
+cleanup:
+numaDestroy(&naw);
+numaDestroy(&nah);
+for (i = 0; i < nim; i++)
+numaaDestroy(&n3a[i]);
+LEPT_FREE(n3a);
+return 0;
+}
+/*!
+* \brief   pixComparePhotoRegionsByHisto()
+*
+* \param[in]    pix1, pix2    any depth; colormap OK
+* \param[in]    box1, box2    [optional] photo regions from each; can be null
+* \param[in]    minratio      requiring sizes be compatible; < 1.0
+* \param[in]    factor        subsampling factor; >= 1
+* \param[in]    n             in range {1, ... 7}. n^2 is the maximum number
+*                             of subregions for histograms; typ. n = 3.
+* \param[out]   pscore        similarity score of histograms
+* \param[in]    debugflag     1 for debug output; 0 for no debugging
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This function compares two grayscale photo regions.  If a
+*          box is given, the region is clipped; otherwise assume
+*          the entire images are photo regions.  This is done with a
+*          set of not more than n^2 spatially aligned histograms, which are
+*          aligned using the centroid of the inverse image.
+*      (2) The parameter %n specifies the "side" of an n x n grid
+*          of subimages.  If the subimages have an aspect ratio larger
+*          than 2, the grid will change, using n^2 as a maximum for
+*          the number of subimages.  For example, if n == 3, but the
+*          image is 600 x 200 pixels, a 3x3 grid would have subimages
+*          of 200 x 67 pixels, which is more than 2:1, so we change
+*          to a 4x2 grid where each subimage has 150 x 100 pixels.
+*      (3) An initial filter gives %score = 0 if the ratio of widths
+*          and heights (smallest / largest) does not exceed a
+*          threshold %minratio.  This must be between 0.5 and 1.0.
+*          If set at 1.0, both images must be exactly the same size.
+*          A typical value for %minratio is 0.9.
+*      (4) Because this function should not be used on text or
+*          line graphics, which can give false positive results
+*          (i.e., high scores for different images), filter the images
+*          using pixGenPhotoHistos(), which returns tiled histograms
+*          only if an image is not text and comparison is expected
+*          to work with histograms.  If either image fails the test,
+*          the comparison returns a score of 0.0.
+*      (5) The white value counts in the histograms are removed; they
+*          are typically pixels that were padded to achieve alignment.
+*      (6) For an efficient representation of the histogram, normalize
+*          using a multiplicative factor so that the number in the
+*          maximum bucket is 255.  It then takes 256 bytes to store.
+*      (7) When comparing the histograms of two regions, use the
+*          Earth Mover distance (EMD), with the histograms normalized
+*          so that the sum over bins is the same.  Further normalize
+*          by dividing by 255, so that the result is in [0.0 ... 1.0].
+*      (8) Get a similarity score S = 1.0 - k * D, where
+*            k is a constant, say in the range 5-10
+*            D = normalized EMD
+*          and for multiple tiles, take the Min(S) to be the final score.
+*          Using aligned tiles gives protection against accidental
+*          similarity of the overall grayscale histograms.
+*          A small number of aligned tiles works well.
+*      (9) With debug on, you get a pdf that shows, for each tile,
+*          the images, histograms and score.
+* </pre>
+*/
+l_ok
+pixComparePhotoRegionsByHisto(PIX        *pix1,
+PIX        *pix2,
+BOX        *box1,
+BOX        *box2,
+l_float32   minratio,
+l_int32     factor,
+l_int32     n,
+l_float32  *pscore,
+l_int32     debugflag)
+{
+l_int32    w1, h1, w2, h2, w1c, h1c, w2c, h2c, debugindex;
+l_float32  wratio, hratio;
+NUMAA     *naa1, *naa2;
+PIX       *pix3, *pix4;
+PIXA      *pixa;
+if (!pscore)
+return ERROR_INT("&score not defined", __func__, 1);
+*pscore = 0.0;
+if (!pix1 || !pix2)
+return ERROR_INT("pix1 and pix2 not both defined", __func__, 1);
+if (minratio < 0.5 || minratio > 1.0)
+return ERROR_INT("minratio not in [0.5 ... 1.0]", __func__, 1);
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (n < 1 || n > 7) {
+L_WARNING("n = %d is invalid; setting to 4\n", __func__, n);
+n = 4;
+}
+debugindex = 0;
+if (debugflag) {
+lept_mkdir("lept/comp");
+debugindex = 666;  /* arbitrary number used for naming output */
+}
+/* Initial filter by size */
+if (box1)
+boxGetGeometry(box1, NULL, NULL, &w1, &h1);
+else
+pixGetDimensions(pix1, &w1, &h1, NULL);
+if (box2)
+boxGetGeometry(box2, NULL, NULL, &w2, &h2);
+else
+pixGetDimensions(pix1, &w2, &h2, NULL);
+wratio = (w1 < w2) ? (l_float32)w1 / (l_float32)w2 :
+(l_float32)w2 / (l_float32)w1;
+hratio = (h1 < h2) ? (l_float32)h1 / (l_float32)h2 :
+(l_float32)h2 / (l_float32)h1;
+if (wratio < minratio || hratio < minratio)
+return 0;
+/* Initial crop, if necessary, and make histos */
+if (box1)
+pix3 = pixClipRectangle(pix1, box1, NULL);
+else
+pix3 = pixClone(pix1);
+pixGenPhotoHistos(pix3, NULL, factor, 0, n, &naa1, &w1c, &h1c, debugindex);
+pixDestroy(&pix3);
+if (!naa1) return 0;
+if (box2)
+pix4 = pixClipRectangle(pix2, box2, NULL);
+else
+pix4 = pixClone(pix2);
+pixGenPhotoHistos(pix4, NULL, factor, 0, n, &naa2, &w2c, &h2c, debugindex);
+pixDestroy(&pix4);
+if (!naa2) return 0;
+/* Compare histograms */
+pixa = (debugflag) ? pixaCreate(0) : NULL;
+compareTilesByHisto(naa1, naa2, minratio, w1c, h1c, w2c, h2c, pscore, pixa);
+pixaDestroy(&pixa);
+return 0;
+}
+/*!
+* \brief   pixGenPhotoHistos()
+*
+* \param[in]    pixs      depth > 1 bpp; colormap OK
+* \param[in]    box       [optional] region to be selected; can be null
+* \param[in]    factor    subsampling; >= 1
+* \param[in]    thresh    threshold for photo/text; use 0 for default
+* \param[in]    n         in range {1, ... 7}. n^2 is the maximum number
+*                         of subregions for histograms; typ. n = 3.
+* \param[out]   pnaa      nx * ny 256-entry gray histograms
+* \param[out]   pw        width of image used to make histograms
+* \param[out]   ph        height of image used to make histograms
+* \param[in]    debugindex  0 for no debugging; positive integer otherwise
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This crops and converts to 8 bpp if necessary.  It adds a
+*          minimal white boundary such that the centroid of the
+*          photo-inverted image is in the center. This allows
+*          automatic alignment with histograms of other image regions.
+*      (2) The parameter %n specifies the "side" of the n x n grid
+*          of subimages.  If the subimages have an aspect ratio larger
+*          than 2, the grid will change, using n^2 as a maximum for
+*          the number of subimages.  For example, if n == 3, but the
+*          image is 600 x 200 pixels, a 3x3 grid would have subimages
+*          of 200 x 67 pixels, which is more than 2:1, so we change
+*          to a 4x2 grid where each subimage has 150 x 100 pixels.
+*      (3) The white value in the histogram is removed, because of
+*          the padding.
+*      (4) Use 0 for conservative default (1.3) for thresh.
+*      (5) For an efficient representation of the histogram, normalize
+*          using a multiplicative factor so that the number in the
+*          maximum bucket is 255.  It then takes 256 bytes to store.
+*      (6) With %debugindex > 0, this makes a pdf that shows, for each tile,
+*          the images and histograms.
+* </pre>
+*/
+l_ok
+pixGenPhotoHistos(PIX        *pixs,
+BOX        *box,
+l_int32     factor,
+l_float32   thresh,
+l_int32     n,
+NUMAA     **pnaa,
+l_int32    *pw,
+l_int32    *ph,
+l_int32     debugindex)
+{
+char    buf[64];
+NUMAA  *naa;
+PIX    *pix1, *pix2, *pix3, *pixm;
+PIXA   *pixa;
+if (pnaa) *pnaa = NULL;
+if (pw) *pw = 0;
+if (ph) *ph = 0;
+if (!pnaa)
+return ERROR_INT("&naa not defined", __func__, 1);
+if (!pw || !ph)
+return ERROR_INT("&w and &h not both defined", __func__, 1);
+if (!pixs || pixGetDepth(pixs) == 1)
+return ERROR_INT("pixs not defined or 1 bpp", __func__, 1);
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (thresh <= 0.0) thresh = 1.3f;  /* default */
+if (n < 1 || n > 7) {
+L_WARNING("n = %d is invalid; setting to 4\n", __func__, n);
+n = 4;
+}
+pixa = NULL;
+if (debugindex > 0) {
+pixa = pixaCreate(0);
+lept_mkdir("lept/comp");
+}
+/* Initial crop, if necessary */
+if (box)
+pix1 = pixClipRectangle(pixs, box, NULL);
+else
+pix1 = pixClone(pixs);
+/* Convert to 8 bpp and pad to center the centroid */
+pix2 = pixConvertTo8(pix1, FALSE);
+pix3 = pixPadToCenterCentroid(pix2, factor);
+/* Set to 255 all pixels above 230.  Do this so that light gray
+* pixels do not enter into the comparison. */
+pixm = pixThresholdToBinary(pix3, 230);
+pixInvert(pixm, pixm);
+pixSetMaskedGeneral(pix3, pixm, 255, 0, 0);
+pixDestroy(&pixm);
+if (debugindex > 0) {
+PIX   *pix4, *pix5, *pix6, *pix7, *pix8;
+PIXA  *pixa2;
+pix4 = pixConvertTo32(pix2);
+pix5 = pixConvertTo32(pix3);
+pix6 = pixScaleToSize(pix4, 400, 0);
+pix7 = pixScaleToSize(pix5, 400, 0);
+pixa2 = pixaCreate(2);
+pixaAddPix(pixa2, pix6, L_INSERT);
+pixaAddPix(pixa2, pix7, L_INSERT);
+pix8 = pixaDisplayTiledInRows(pixa2, 32, 1000, 1.0, 0, 50, 3);
+pixaAddPix(pixa, pix8, L_INSERT);
+pixDestroy(&pix4);
+pixDestroy(&pix5);
+pixaDestroy(&pixa2);
+}
+pixDestroy(&pix1);
+pixDestroy(&pix2);
+/* Test if this is a photoimage */
+pixDecideIfPhotoImage(pix3, factor, thresh, n, &naa, pixa);
+if (naa) {
+*pnaa = naa;
+*pw = pixGetWidth(pix3);
+*ph = pixGetHeight(pix3);
+}
+if (pixa) {
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/tiledhistos.%d.pdf",
+debugindex);
+lept_stderr("Writing to %s\n", buf);
+pixaConvertToPdf(pixa, 300, 1.0, L_FLATE_ENCODE, 0, NULL, buf);
+pixaDestroy(&pixa);
+}
+pixDestroy(&pix3);
+return 0;
+}
+/*!
+* \brief   pixPadToCenterCentroid()
+*
+* \param[in]    pixs     any depth, colormap OK
+* \param[in]    factor   subsampling for centroid; >= 1
+* \return  pixd padded with white pixels, or NULL on error.
+*
+* <pre>
+* Notes:
+*      (1) This add minimum white padding to an 8 bpp pix, such that
+*          the centroid of the photometric inverse is in the center of
+*          the resulting image.  Thus in computing the centroid,
+*          black pixels have weight 255, and white pixels have weight 0.
+* </pre>
+*/
+PIX *
+pixPadToCenterCentroid(PIX     *pixs,
+l_int32  factor)
+{
+l_float32  cx, cy;
+l_int32    xs, ys, delx, dely, icx, icy, ws, hs, wd, hd;
+PIX       *pix1, *pixd;
+if (!pixs)
+return (PIX *)ERROR_PTR("pixs not defined", __func__, NULL);
+if (factor < 1)
+return (PIX *)ERROR_PTR("invalid sampling factor", __func__, NULL);
+pix1 = pixConvertTo8(pixs, FALSE);
+pixCentroid8(pix1, factor, &cx, &cy);
+icx = (l_int32)(cx + 0.5);
+icy = (l_int32)(cy + 0.5);
+pixGetDimensions(pix1, &ws, &hs, NULL);
+delx = ws - 2 * icx;
+dely = hs - 2 * icy;
+xs = L_MAX(0, delx);
+ys = L_MAX(0, dely);
+wd = 2 * L_MAX(icx, ws - icx);
+hd = 2 * L_MAX(icy, hs - icy);
+pixd = pixCreate(wd, hd, 8);
+pixSetAll(pixd);  /* to white */
+pixCopyResolution(pixd, pixs);
+pixRasterop(pixd, xs, ys, ws, hs, PIX_SRC, pix1, 0, 0);
+pixDestroy(&pix1);
+return pixd;
+}
+/*!
+* \brief   pixCentroid8()
+*
+* \param[in]    pixs    8 bpp
+* \param[in]    factor  subsampling factor; >= 1
+* \param[out]   pcx     x value of centroid
+* \param[out]   pcy     y value of centroid
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This first does a photometric inversion (black = 255, white = 0).
+*          It then finds the centroid of the result.  The inversion is
+*          done because white is usually background, so the centroid
+*          is computed based on the "foreground" gray pixels, and the
+*          darker the pixel, the more weight it is given.
+* </pre>
+*/
+l_ok
+pixCentroid8(PIX        *pixs,
+l_int32     factor,
+l_float32  *pcx,
+l_float32  *pcy)
+{
+l_int32    i, j, w, h, wpl, val;
+l_float32  sumx, sumy, sumv;
+l_uint32  *data, *line;
+PIX       *pix1;
+if (pcx) *pcx = 0.0;
+if (pcy) *pcy = 0.0;
+if (!pixs || pixGetDepth(pixs) != 8)
+return ERROR_INT("pixs undefined or not 8 bpp", __func__, 1);
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (!pcx || !pcy)
+return ERROR_INT("&cx and &cy not both defined", __func__, 1);
+pix1 = pixInvert(NULL, pixs);
+pixGetDimensions(pix1, &w, &h, NULL);
+data = pixGetData(pix1);
+wpl = pixGetWpl(pix1);
+sumx = sumy = sumv = 0.0;
+for (i = 0; i < h; i++) {
+line = data + i * wpl;
+for (j = 0; j < w; j++) {
+val = GET_DATA_BYTE(line, j);
+sumx += val * j;
+sumy += val * i;
+sumv += val;
+}
+}
+pixDestroy(&pix1);
+if (sumv == 0) {
+L_INFO("input image is white\n", __func__);
+*pcx = (l_float32)(w) / 2;
+*pcy = (l_float32)(h) / 2;
+} else {
+*pcx = sumx / sumv;
+*pcy = sumy / sumv;
+}
+return 0;
+}
+/*!
+* \brief   pixDecideIfPhotoImage()
+*
+* \param[in]    pix         8 bpp, centroid in center
+* \param[in]    factor      subsampling for histograms; >= 1
+* \param[in]    thresh      threshold for photo/text; use 0 for default
+* \param[in]    n           in range {1, ... 7}. n^2 is the maximum number
+*                           of subregions for histograms; typ. n = 3.
+* \param[out]   pnaa        array of normalized histograms
+* \param[in]    pixadebug   [optional] use only for debug output
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) The input image must be 8 bpp (no colormap), and padded with
+*          white pixels so the centroid of photo-inverted pixels is at
+*          the center of the image.
+*      (2) The parameter %n specifies the "side" of the n x n grid
+*          of subimages.  If the subimages have an aspect ratio larger
+*          than 2, the grid will change, using n^2 as a maximum for
+*          the number of subimages.  For example, if n == 3, but the
+*          image is 600 x 200 pixels, a 3x3 grid would have subimages
+*          of 200 x 67 pixels, which is more than 2:1, so we change
+*          to a 4x2 grid where each subimage has 150 x 100 pixels.
+*      (3) If the pix is not almost certainly a photoimage, the returned
+*          histograms (%naa) are null.
+*      (4) If histograms are generated, the white (255) count is set
+*          to 0.  This removes all pixels values above 230, including
+*          white padding from the centroid matching operation, from
+*          consideration.  The resulting histograms are then normalized
+*          so the maximum count is 255.
+*      (5) Default for %thresh is 1.3; this seems sufficiently conservative.
+*      (6) Use %pixadebug == NULL unless debug output is requested.
+* </pre>
+*/
+l_ok
+pixDecideIfPhotoImage(PIX       *pix,
+l_int32    factor,
+l_float32  thresh,
+l_int32    n,
+NUMAA    **pnaa,
+PIXA      *pixadebug)
+{
+char       buf[64];
+l_int32    i, w, h, nx, ny, ngrids, istext, isphoto;
+l_float32  maxval, sum1, sum2, ratio;
+L_BMF     *bmf;
+NUMA      *na1, *na2, *na3, *narv;
+NUMAA     *naa;
+PIX       *pix1;
+PIXA      *pixa1, *pixa2, *pixa3;
+if (!pnaa)
+return ERROR_INT("&naa not defined", __func__, 1);
+*pnaa = NULL;
+if (!pix || pixGetDepth(pix) != 8 || pixGetColormap(pix))
+return ERROR_INT("pix undefined or invalid", __func__, 1);
+if (n < 1 || n > 7) {
+L_WARNING("n = %d is invalid; setting to 4\n", __func__, n);
+n = 4;
+}
+if (thresh <= 0.0) thresh = 1.3f;  /* default */
+/* Look for text lines */
+pixDecideIfText(pix, NULL, &istext, pixadebug);
+if (istext) {
+L_INFO("Image is text\n", __func__);
+return 0;
+}
+/* Determine grid from n */
+pixGetDimensions(pix, &w, &h, NULL);
+if (w == 0 || h == 0)
+return ERROR_INT("invalid pix dimension", __func__, 1);
+findHistoGridDimensions(n, w, h, &nx, &ny, 1);
+/* Evaluate histograms in each tile */
+pixa1 = pixaSplitPix(pix, nx, ny, 0, 0);
+ngrids = nx * ny;
+bmf = (pixadebug) ? bmfCreate(NULL, 6) : NULL;
+naa = numaaCreate(ngrids);
+if (pixadebug) {
+lept_rmdir("lept/compplot");
+lept_mkdir("lept/compplot");
+}
+for (i = 0; i < ngrids; i++) {
+pix1 = pixaGetPix(pixa1, i, L_CLONE);
+/* Get histograms, set white count to 0, normalize max to 255 */
+na1 = pixGetGrayHistogram(pix1, factor);
+numaSetValue(na1, 255, 0);
+na2 = numaWindowedMean(na1, 5);  /* do some smoothing */
+numaGetMax(na2, &maxval, NULL);
+na3 = numaTransform(na2, 0, 255.0 / maxval);
+if (pixadebug) {
+snprintf(buf, sizeof(buf), "/tmp/lept/compplot/plot.%d", i);
+gplotSimple1(na3, GPLOT_PNG, buf, "Histos");
+}
+numaaAddNuma(naa, na3, L_INSERT);
+numaDestroy(&na1);
+numaDestroy(&na2);
+pixDestroy(&pix1);
+}
+if (pixadebug) {
+pix1 = pixaDisplayTiledInColumns(pixa1, nx, 1.0, 30, 2);
+pixaAddPix(pixadebug, pix1, L_INSERT);
+pixa2 = pixaReadFiles("/tmp/lept/compplot", ".png");
+pixa3 = pixaScale(pixa2, 0.4f, 0.4f);
+pix1 = pixaDisplayTiledInColumns(pixa3, nx, 1.0, 30, 2);
+pixaAddPix(pixadebug, pix1, L_INSERT);
+pixaDestroy(&pixa2);
+pixaDestroy(&pixa3);
+}
+/* Compute the standard deviation between these histos to decide
+* if the image is photo or something more like line art,
+* which does not support good comparison by tiled histograms.  */
+grayInterHistogramStats(naa, 5, NULL, NULL, NULL, &narv);
+/* For photos, the root variance has a larger weight of
+* values in the range [50 ... 150] compared to [200 ... 230],
+* than text or line art.  For the latter, most of the variance
+* between tiles is in the lightest parts of the image, well
+* above 150.  */
+numaGetSumOnInterval(narv, 50, 150, &sum1);
+numaGetSumOnInterval(narv, 200, 230, &sum2);
+if (sum2 == 0.0) {  /* shouldn't happen */
+ratio = 0.001f;  /* anything very small for debug output */
+isphoto = 0;  /* be conservative */
+} else {
+ratio = sum1 / sum2;
+isphoto = (ratio > thresh) ? 1 : 0;
+}
+if (pixadebug) {
+if (isphoto)
+L_INFO("ratio %f > %f; isphoto is true\n",
+__func__, ratio, thresh);
+else
+L_INFO("ratio %f < %f; isphoto is false\n",
+__func__, ratio, thresh);
+}
+if (isphoto)
+*pnaa = naa;
+else
+numaaDestroy(&naa);
+bmfDestroy(&bmf);
+numaDestroy(&narv);
+pixaDestroy(&pixa1);
+return 0;
+}
+/*!
+* \brief   findHistoGridDimensions()
+*
+* \param[in]    n         max number of grid elements is n^2; typ. n = 3
+* \param[in]    w         width of image to be subdivided
+* \param[in]    h         height of image to be subdivided
+* \param[out]   pnx       number of grid elements in x direction
+* \param[out]   pny       number of grid elements in y direction
+* \param[in]    debug     1 for debug output to stderr
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This determines the number of subdivisions to be used on
+*          the image in each direction.  A histogram will be built
+*          for each subimage.
+*      (2) The parameter %n specifies the "side" of the n x n grid
+*          of subimages.  If the subimages have an aspect ratio larger
+*          than 2, the grid will change, using n^2 as a maximum for
+*          the number of subimages.  For example, if n == 3, but the
+*          image is 600 x 200 pixels, a 3x3 grid would have subimages
+*          of 200 x 67 pixels, which is more than 2:1, so we change
+*          to a 4x2 grid where each subimage has 150 x 100 pixels.
+* </pre>
+*/
+static l_ok
+findHistoGridDimensions(l_int32   n,
+l_int32   w,
+l_int32   h,
+l_int32  *pnx,
+l_int32  *pny,
+l_int32   debug)
+{
+l_int32    nx, ny, max;
+l_float32  ratio;
+ratio = (l_float32)w / (l_float32)h;
+max = n * n;
+nx = ny = n;
+while (nx > 1 && ny > 1) {
+if (ratio > 2.0) {  /* reduce ny */
+ny--;
+nx = max / ny;
+if (debug)
+lept_stderr("nx = %d, ny = %d, ratio w/h = %4.2f\n",
+nx, ny, ratio);
+} else if (ratio < 0.5) {  /* reduce nx */
+nx--;
+ny = max / nx;
+if (debug)
+lept_stderr("nx = %d, ny = %d, ratio w/h = %4.2f\n",
+nx, ny, ratio);
+} else {  /* we're ok */
+if (debug)
+lept_stderr("nx = %d, ny = %d, ratio w/h = %4.2f\n",
+nx, ny, ratio);
+break;
+}
+ratio = (l_float32)(ny * w) / (l_float32)(nx * h);
+}
+*pnx = nx;
+*pny = ny;
+return 0;
+}
+/*!
+* \brief   compareTilesByHisto()
+*
+* \param[in]    naa1, naa2      each is a set of 256 entry histograms
+* \param[in]    minratio        requiring image sizes be compatible; < 1.0
+* \param[in]    w1, h1, w2, h2  image sizes from which histograms were made
+* \param[out]   pscore          similarity score of histograms
+* \param[in]    pixadebug       [optional] use only for debug output
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) naa1 and naa2 must be generated using pixGenPhotoHistos(),
+*          using the same tile sizes.
+*      (2) The image dimensions must be similar.  The score is 0.0
+*          if the ratio of widths and heights (smallest / largest)
+*          exceeds a threshold %minratio, which must be between
+*          0.5 and 1.0.  If set at 1.0, both images must be exactly
+*          the same size.  A typical value for %minratio is 0.9.
+*      (3) The input pixadebug is null unless debug output is requested.
+* </pre>
+*/
+l_ok
+compareTilesByHisto(NUMAA      *naa1,
+NUMAA      *naa2,
+l_float32   minratio,
+l_int32     w1,
+l_int32     h1,
+l_int32     w2,
+l_int32     h2,
+l_float32  *pscore,
+PIXA       *pixadebug)
+{
+char       buf1[128], buf2[128];
+l_int32    i, n;
+l_float32  wratio, hratio, score, minscore, dist;
+L_BMF     *bmf;
+NUMA      *na1, *na2, *nadist, *nascore;
+if (!pscore)
+return ERROR_INT("&score not defined", __func__, 1);
+*pscore = 0.0;
+if (!naa1 || !naa2)
+return ERROR_INT("naa1 and naa2 not both defined", __func__, 1);
+/* Filter for different sizes */
+wratio = (w1 < w2) ? (l_float32)w1 / (l_float32)w2 :
+(l_float32)w2 / (l_float32)w1;
+hratio = (h1 < h2) ? (l_float32)h1 / (l_float32)h2 :
+(l_float32)h2 / (l_float32)h1;
+if (wratio < minratio || hratio < minratio) {
+if (pixadebug)
+L_INFO("Sizes differ: wratio = %f, hratio = %f\n",
+__func__, wratio, hratio);
+return 0;
+}
+n = numaaGetCount(naa1);
+if (n != numaaGetCount(naa2)) {  /* due to differing w/h ratio */
+L_INFO("naa1 and naa2 sizes are different\n", __func__);
+return 0;
+}
+if (pixadebug) {
+lept_rmdir("lept/comptile");
+lept_mkdir("lept/comptile");
+}
+/* Evaluate histograms in each tile.  Remove white before
+* computing EMD, because there are may be a lot of white
+* pixels due to padding, and we don't want to include them.
+* This also makes the debug histo plots more informative. */
+minscore = 1.0;
+nadist = numaCreate(n);
+nascore = numaCreate(n);
+bmf = (pixadebug) ? bmfCreate(NULL, 6) : NULL;
+for (i = 0; i < n; i++) {
+na1 = numaaGetNuma(naa1, i, L_CLONE);
+na2 = numaaGetNuma(naa2, i, L_CLONE);
+numaSetValue(na1, 255, 0.0);
+numaSetValue(na2, 255, 0.0);
+/* To compare histograms, use the normalized earthmover distance.
+* Further normalize to get the EM distance as a fraction of the
+* maximum distance in the histogram (255).  Finally, scale this
+* up by 10.0, and subtract from 1.0 to get a similarity score. */
+numaEarthMoverDistance(na1, na2, &dist);
+score = L_MAX(0.0, 1.0 - 10.0 * (dist / 255.));
+numaAddNumber(nadist, dist);
+numaAddNumber(nascore, score);
+minscore = L_MIN(minscore, score);
+if (pixadebug) {
+snprintf(buf1, sizeof(buf1), "/tmp/lept/comptile/plot.%d", i);
+gplotSimple2(na1, na2, GPLOT_PNG, buf1, "Histos");
+}
+numaDestroy(&na1);
+numaDestroy(&na2);
+}
+*pscore = minscore;
+if (pixadebug) {
+for (i = 0; i < n; i++) {
+PIX  *pix1, *pix2;
+snprintf(buf1, sizeof(buf1), "/tmp/lept/comptile/plot.%d.png", i);
+pix1 = pixRead(buf1);
+numaGetFValue(nadist, i, &dist);
+numaGetFValue(nascore, i, &score);
+snprintf(buf2, sizeof(buf2),
+"Image %d\ndist = %5.3f, score = %5.3f", i, dist, score);
+pix2 = pixAddTextlines(pix1, bmf, buf2, 0x0000ff00, L_ADD_BELOW);
+pixaAddPix(pixadebug, pix2, L_INSERT);
+pixDestroy(&pix1);
+}
+lept_stderr("Writing to /tmp/lept/comptile/comparegray.pdf\n");
+pixaConvertToPdf(pixadebug, 300, 1.0, L_FLATE_ENCODE, 0, NULL,
+"/tmp/lept/comptile/comparegray.pdf");
+numaWriteDebug("/tmp/lept/comptile/scores.na", nascore);
+numaWriteDebug("/tmp/lept/comptile/dists.na", nadist);
+}
+bmfDestroy(&bmf);
+numaDestroy(&nadist);
+numaDestroy(&nascore);
+return 0;
+}
+/*!
+* \brief   pixCompareGrayByHisto()
+*
+* \param[in]    pix1, pix2  any depth; colormap OK
+* \param[in]    box1, box2  [optional] region selected from each; can be null
+* \param[in]    minratio    requiring sizes be compatible; < 1.0
+* \param[in]    maxgray     max value to keep in histo; >= 200, 255 to keep all
+* \param[in]    factor      subsampling factor; >= 1
+* \param[in]    n           in range {1, ... 7}. n^2 is the maximum number
+*                           of subregions for histograms; typ. n = 3.
+* \param[out]   pscore      similarity score of histograms
+* \param[in]    debugflag   1 for debug output; 0 for no debugging
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This function compares two grayscale photo regions.  It can
+*          do it with a single histogram from each region, or with a
+*          set of spatially aligned histograms.  For both cases,
+*          align the regions using the centroid of the inverse image,
+*          and crop to the smallest of the two.
+*      (2) The parameter %n specifies the "side" of an n x n grid
+*          of subimages.  If the subimages have an aspect ratio larger
+*          than 2, the grid will change, using n^2 as a maximum for
+*          the number of subimages.  For example, if n == 3, but the
+*          image is 600 x 200 pixels, a 3x3 grid would have subimages
+*          of 200 x 67 pixels, which is more than 2:1, so we change
+*          to a 4x2 grid where each subimage has 150 x 100 pixels.
+*      (3) An initial filter gives %score = 0 if the ratio of widths
+*          and heights (smallest / largest) does not exceed a
+*          threshold %minratio.  This must be between 0.5 and 1.0.
+*          If set at 1.0, both images must be exactly the same size.
+*          A typical value for %minratio is 0.9.
+*      (4) The lightest values in the histogram can be disregarded.
+*          Set %maxgray to the lightest value to be kept.  For example,
+*          to eliminate white (255), set %maxgray = 254.  %maxgray must
+*          be >= 200.
+*      (5) For an efficient representation of the histogram, normalize
+*          using a multiplicative factor so that the number in the
+*          maximum bucket is 255.  It then takes 256 bytes to store.
+*      (6) When comparing the histograms of two regions:
+*          ~ Use %maxgray = 254 to ignore the white pixels, the number
+*            of which may be sensitive to the crop region if the pixels
+*            outside that region are white.
+*          ~ Use the Earth Mover distance (EMD), with the histograms
+*            normalized so that the sum over bins is the same.
+*            Further normalize by dividing by 255, so that the result
+*            is in [0.0 ... 1.0].
+*      (7) Get a similarity score S = 1.0 - k * D, where
+*            k is a constant, say in the range 5-10
+*            D = normalized EMD
+*          and for multiple tiles, take the Min(S) to be the final score.
+*          Using aligned tiles gives protection against accidental
+*          similarity of the overall grayscale histograms.
+*          A small number of aligned tiles works well.
+*      (8) With debug on, you get a pdf that shows, for each tile,
+*          the images, histograms and score.
+*      (9) When to use:
+*          (a) Because this function should not be used on text or
+*              line graphics, which can give false positive results
+*              (i.e., high scores for different images), the input
+*              images should be filtered.
+*          (b) To filter, first use pixDecideIfText().  If that function
+*              says the image is text, do not use it.  If the function
+*              says it is not text, it still may be line graphics, and
+*              in that case, use:
+*                 pixGetGrayHistogramTiled()
+*                 grayInterHistogramStats()
+*              to determine whether it is photo or line graphics.
+* </pre>
+*/
+l_ok
+pixCompareGrayByHisto(PIX        *pix1,
+PIX        *pix2,
+BOX        *box1,
+BOX        *box2,
+l_float32   minratio,
+l_int32     maxgray,
+l_int32     factor,
+l_int32     n,
+l_float32  *pscore,
+l_int32     debugflag)
+{
+l_int32    w1, h1, w2, h2;
+l_float32  wratio, hratio;
+BOX       *box3, *box4;
+PIX       *pix3, *pix4, *pix5, *pix6, *pix7, *pix8;
+PIXA      *pixa;
+if (!pscore)
+return ERROR_INT("&score not defined", __func__, 1);
+*pscore = 0.0;
+if (!pix1 || !pix2)
+return ERROR_INT("pix1 and pix2 not both defined", __func__, 1);
+if (minratio < 0.5 || minratio > 1.0)
+return ERROR_INT("minratio not in [0.5 ... 1.0]", __func__, 1);
+if (maxgray < 200)
+return ERROR_INT("invalid maxgray; should be >= 200", __func__, 1);
+maxgray = L_MIN(255, maxgray);
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (n < 1 || n > 7) {
+L_WARNING("n = %d is invalid; setting to 4\n", __func__, n);
+n = 4;
+}
+if (debugflag)
+lept_mkdir("lept/comp");
+/* Initial filter by size */
+if (box1)
+boxGetGeometry(box1, NULL, NULL, &w1, &h1);
+else
+pixGetDimensions(pix1, &w1, &h1, NULL);
+if (box2)
+boxGetGeometry(box2, NULL, NULL, &w2, &h2);
+else
+pixGetDimensions(pix1, &w2, &h2, NULL);
+wratio = (w1 < w2) ? (l_float32)w1 / (l_float32)w2 :
+(l_float32)w2 / (l_float32)w1;
+hratio = (h1 < h2) ? (l_float32)h1 / (l_float32)h2 :
+(l_float32)h2 / (l_float32)h1;
+if (wratio < minratio || hratio < minratio)
+return 0;
+/* Initial crop, if necessary */
+if (box1)
+pix3 = pixClipRectangle(pix1, box1, NULL);
+else
+pix3 = pixClone(pix1);
+if (box2)
+pix4 = pixClipRectangle(pix2, box2, NULL);
+else
+pix4 = pixClone(pix2);
+/* Convert to 8 bpp, align centroids and do maximal crop */
+pix5 = pixConvertTo8(pix3, FALSE);
+pix6 = pixConvertTo8(pix4, FALSE);
+pixCropAlignedToCentroid(pix5, pix6, factor, &box3, &box4);
+pix7 = pixClipRectangle(pix5, box3, NULL);
+pix8 = pixClipRectangle(pix6, box4, NULL);
+pixa = (debugflag) ? pixaCreate(0) : NULL;
+if (debugflag) {
+PIX     *pix9, *pix10, *pix11, *pix12, *pix13;
+PIXA    *pixa2;
+pix9 = pixConvertTo32(pix5);
+pix10 = pixConvertTo32(pix6);
+pixRenderBoxArb(pix9, box3, 2, 255, 0, 0);
+pixRenderBoxArb(pix10, box4, 2, 255, 0, 0);
+pix11 = pixScaleToSize(pix9, 400, 0);
+pix12 = pixScaleToSize(pix10, 400, 0);
+pixa2 = pixaCreate(2);
+pixaAddPix(pixa2, pix11, L_INSERT);
+pixaAddPix(pixa2, pix12, L_INSERT);
+pix13 = pixaDisplayTiledInRows(pixa2, 32, 1000, 1.0, 0, 50, 0);
+pixaAddPix(pixa, pix13, L_INSERT);
+pixDestroy(&pix9);
+pixDestroy(&pix10);
+pixaDestroy(&pixa2);
+}
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+pixDestroy(&pix5);
+pixDestroy(&pix6);
+boxDestroy(&box3);
+boxDestroy(&box4);
+/* Tile and compare histograms */
+pixCompareTilesByHisto(pix7, pix8, maxgray, factor, n, pscore, pixa);
+pixaDestroy(&pixa);
+pixDestroy(&pix7);
+pixDestroy(&pix8);
+return 0;
+}
+/*!
+* \brief   pixCompareTilesByHisto()
+*
+* \param[in]    pix1, pix2     8 bpp
+* \param[in]    maxgray        max value to keep in histo; 255 to keep all
+* \param[in]    factor         subsampling factor; >= 1
+* \param[in]    n              see pixCompareGrayByHisto()
+* \param[out]   pscore         similarity score of histograms
+* \param[in]    pixadebug      [optional] use only for debug output
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This static function is only called from pixCompareGrayByHisto().
+*          The input images have been converted to 8 bpp if necessary,
+*          aligned and cropped.
+*      (2) The input pixadebug is null unless debug output is requested.
+*      (3) See pixCompareGrayByHisto() for details.
+* </pre>
+*/
+static l_ok
+pixCompareTilesByHisto(PIX        *pix1,
+PIX        *pix2,
+l_int32     maxgray,
+l_int32     factor,
+l_int32     n,
+l_float32  *pscore,
+PIXA       *pixadebug)
+{
+char       buf[64];
+l_int32    w, h, i, j, nx, ny, ngr;
+l_float32  score, minscore, maxval1, maxval2, dist;
+L_BMF     *bmf;
+NUMA      *na1, *na2, *na3, *na4, *na5, *na6, *na7;
+PIX       *pix3, *pix4;
+PIXA      *pixa1, *pixa2;
+if (!pscore)
+return ERROR_INT("&score not defined", __func__, 1);
+*pscore = 0.0;
+if (!pix1 || !pix2)
+return ERROR_INT("pix1 and pix2 not both defined", __func__, 1);
+/* Determine grid from n */
+pixGetDimensions(pix1, &w, &h, NULL);
+findHistoGridDimensions(n, w, h, &nx, &ny, 1);
+ngr = nx * ny;
+/* Evaluate histograms in each tile */
+pixa1 = pixaSplitPix(pix1, nx, ny, 0, 0);
+pixa2 = pixaSplitPix(pix2, nx, ny, 0, 0);
+na7 = (pixadebug) ? numaCreate(ngr) : NULL;
+bmf = (pixadebug) ? bmfCreate(NULL, 6) : NULL;
+minscore = 1.0;
+for (i = 0; i < ngr; i++) {
+pix3 = pixaGetPix(pixa1, i, L_CLONE);
+pix4 = pixaGetPix(pixa2, i, L_CLONE);
+/* Get histograms, set white count to 0, normalize max to 255 */
+na1 = pixGetGrayHistogram(pix3, factor);
+na2 = pixGetGrayHistogram(pix4, factor);
+if (maxgray < 255) {
+for (j = maxgray + 1; j <= 255; j++) {
+numaSetValue(na1, j, 0);
+numaSetValue(na2, j, 0);
+}
+}
+na3 = numaWindowedMean(na1, 5);
+na4 = numaWindowedMean(na2, 5);
+numaGetMax(na3, &maxval1, NULL);
+numaGetMax(na4, &maxval2, NULL);
+na5 = numaTransform(na3, 0, 255.0 / maxval1);
+na6 = numaTransform(na4, 0, 255.0 / maxval2);
+if (pixadebug) {
+gplotSimple2(na5, na6, GPLOT_PNG, "/tmp/lept/comp/plot1", "Histos");
+}
+/* To compare histograms, use the normalized earthmover distance.
+* Further normalize to get the EM distance as a fraction of the
+* maximum distance in the histogram (255).  Finally, scale this
+* up by 10.0, and subtract from 1.0 to get a similarity score. */
+numaEarthMoverDistance(na5, na6, &dist);
+score = L_MAX(0.0, 1.0 - 8.0 * (dist / 255.));
+if (pixadebug) numaAddNumber(na7, score);
+minscore = L_MIN(minscore, score);
+if (pixadebug) {
+PIX     *pix5, *pix6, *pix7, *pix8, *pix9, *pix10;
+PIXA    *pixa3;
+l_int32  w, h, wscale;
+pixa3 = pixaCreate(3);
+pixGetDimensions(pix3, &w, &h, NULL);
+wscale = (w > h) ? 700 : 400;
+pix5 = pixScaleToSize(pix3, wscale, 0);
+pix6 = pixScaleToSize(pix4, wscale, 0);
+pixaAddPix(pixa3, pix5, L_INSERT);
+pixaAddPix(pixa3, pix6, L_INSERT);
+pix7 = pixRead("/tmp/lept/comp/plot1.png");
+pix8 = pixScaleToSize(pix7, 700, 0);
+snprintf(buf, sizeof(buf), "%5.3f", score);
+pix9 = pixAddTextlines(pix8, bmf, buf, 0x0000ff00, L_ADD_RIGHT);
+pixaAddPix(pixa3, pix9, L_INSERT);
+pix10 = pixaDisplayTiledInRows(pixa3, 32, 1000, 1.0, 0, 50, 0);
+pixaAddPix(pixadebug, pix10, L_INSERT);
+pixDestroy(&pix7);
+pixDestroy(&pix8);
+pixaDestroy(&pixa3);
+}
+numaDestroy(&na1);
+numaDestroy(&na2);
+numaDestroy(&na3);
+numaDestroy(&na4);
+numaDestroy(&na5);
+numaDestroy(&na6);
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+}
+*pscore = minscore;
+if (pixadebug) {
+pixaConvertToPdf(pixadebug, 300, 1.0, L_FLATE_ENCODE, 0, NULL,
+"/tmp/lept/comp/comparegray.pdf");
+numaWriteDebug("/tmp/lept/comp/tilescores.na", na7);
+}
+bmfDestroy(&bmf);
+numaDestroy(&na7);
+pixaDestroy(&pixa1);
+pixaDestroy(&pixa2);
+return 0;
+}
+/*!
+* \brief   pixCropAlignedToCentroid()
+*
+* \param[in]    pix1, pix2   any depth; colormap OK
+* \param[in]    factor       subsampling; >= 1
+* \param[out]   pbox1        crop box for pix1
+* \param[out]   pbox2        crop box for pix2
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This finds the maximum crop boxes for two 8 bpp images when
+*          their centroids of their photometric inverses are aligned.
+*          Black pixels have weight 255; white pixels have weight 0.
+* </pre>
+*/
+l_ok
+pixCropAlignedToCentroid(PIX     *pix1,
+PIX     *pix2,
+l_int32  factor,
+BOX    **pbox1,
+BOX    **pbox2)
+{
+l_float32  cx1, cy1, cx2, cy2;
+l_int32    w1, h1, w2, h2, icx1, icy1, icx2, icy2;
+l_int32    xm, xm1, xm2, xp, xp1, xp2, ym, ym1, ym2, yp, yp1, yp2;
+PIX       *pix3, *pix4;
+if (pbox1) *pbox1 = NULL;
+if (pbox2) *pbox2 = NULL;
+if (!pix1 || !pix2)
+return ERROR_INT("pix1 and pix2 not both defined", __func__, 1);
+if (factor < 1)
+return ERROR_INT("subsampling factor must be >= 1", __func__, 1);
+if (!pbox1 || !pbox2)
+return ERROR_INT("&box1 and &box2 not both defined", __func__, 1);
+pix3 = pixConvertTo8(pix1, FALSE);
+pix4 = pixConvertTo8(pix2, FALSE);
+pixCentroid8(pix3, factor, &cx1, &cy1);
+pixCentroid8(pix4, factor, &cx2, &cy2);
+pixGetDimensions(pix3, &w1, &h1, NULL);
+pixGetDimensions(pix4, &w2, &h2, NULL);
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+icx1 = (l_int32)(cx1 + 0.5);
+icy1 = (l_int32)(cy1 + 0.5);
+icx2 = (l_int32)(cx2 + 0.5);
+icy2 = (l_int32)(cy2 + 0.5);
+xm = L_MIN(icx1, icx2);
+xm1 = icx1 - xm;
+xm2 = icx2 - xm;
+xp = L_MIN(w1 - icx1, w2 - icx2);  /* one pixel beyond to the right */
+xp1 = icx1 + xp;
+xp2 = icx2 + xp;
+ym = L_MIN(icy1, icy2);
+ym1 = icy1 - ym;
+ym2 = icy2 - ym;
+yp = L_MIN(h1 - icy1, h2 - icy2);  /* one pixel below the bottom */
+yp1 = icy1 + yp;
+yp2 = icy2 + yp;
+*pbox1 = boxCreate(xm1, ym1, xp1 - xm1, yp1 - ym1);
+*pbox2 = boxCreate(xm2, ym2, xp2 - xm2, yp2 - ym2);
+return 0;
+}
+/*!
+* \brief   l_compressGrayHistograms()
+*
+* \param[in]    naa     set of 256-entry histograms
+* \param[in]    w, h    size of image
+* \param[out]   psize   size of byte array
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This first writes w and h to the byte array as 4 byte ints.
+*      (2) Then it normalizes each histogram to a max value of 255,
+*          and saves each value as a byte.  If there are
+*          N histograms, the output bytearray has 8 + 256 * N bytes.
+*      (3) Further compression of the array with zlib yields only about
+*          a 25% decrease in size, so we don't bother.  If size reduction
+*          were important, a lossy transform using a 1-dimensional DCT
+*          would be effective, because we don't care about the fine
+*          details of these histograms.
+* </pre>
+*/
+l_uint8 *
+l_compressGrayHistograms(NUMAA   *naa,
+l_int32  w,
+l_int32  h,
+size_t  *psize)
+{
+l_uint8   *bytea;
+l_int32    i, j, n, nn, ival;
+l_float32  maxval;
+NUMA      *na1, *na2;
+if (!psize)
+return (l_uint8 *)ERROR_PTR("&size not defined", __func__, NULL);
+*psize = 0;
+if (!naa)
+return (l_uint8 *)ERROR_PTR("naa not defined", __func__, NULL);
+n = numaaGetCount(naa);
+for (i = 0; i < n; i++) {
+nn = numaaGetNumaCount(naa, i);
+if (nn != 256) {
+L_ERROR("%d numbers in numa[%d]\n", __func__, nn, i);
+return NULL;
+}
+}
+if ((bytea = (l_uint8 *)LEPT_CALLOC(8 + 256 * n, sizeof(l_uint8))) == NULL)
+return (l_uint8 *)ERROR_PTR("bytea not made", __func__, NULL);
+*psize = 8 + 256 * n;
+l_setDataFourBytes(bytea, 0, w);
+l_setDataFourBytes(bytea, 1, h);
+for (i = 0; i < n; i++) {
+na1 = numaaGetNuma(naa, i, L_COPY);
+numaGetMax(na1, &maxval, NULL);
+na2 = numaTransform(na1, 0, 255.0 / maxval);
+for (j = 0; j < 256; j++) {
+numaGetIValue(na2, j, &ival);
+bytea[8 + 256 * i + j] = ival;
+}
+numaDestroy(&na1);
+numaDestroy(&na2);
+}
+return bytea;
+}
+/*!
+* \brief   l_uncompressGrayHistograms()
+*
+* \param[in]    bytea    byte array of size 8 + 256 * N, N an integer
+* \param[in]    size     size of byte array
+* \param[out]   pw       width of the image that generated the histograms
+* \param[out]   ph       height of the image
+* \return  numaa     representing N histograms, each with 256 bins,
+*                    or NULL on error.
+*
+* <pre>
+* Notes:
+*      (1) The first 8 bytes are read as two 32-bit ints.
+*      (2) Then this constructs a numaa representing some number of
+*          gray histograms that are normalized such that the max value
+*          in each histogram is 255.  The data is stored as a byte
+*          array, with 256 bytes holding the data for each histogram.
+*          Each gray histogram was computed from a tile of a grayscale image.
+* </pre>
+*/
+NUMAA *
+l_uncompressGrayHistograms(l_uint8  *bytea,
+size_t    size,
+l_int32  *pw,
+l_int32  *ph)
+{
+l_int32  i, j, n;
+NUMA    *na;
+NUMAA   *naa;
+if (pw) *pw = 0;
+if (ph) *ph = 0;
+if (!pw || !ph)
+return (NUMAA *)ERROR_PTR("&w and &h not both defined", __func__, NULL);
+if (!bytea)
+return (NUMAA *)ERROR_PTR("bytea not defined", __func__, NULL);
+n = (size - 8) / 256;
+if ((size - 8) % 256 != 0)
+return (NUMAA *)ERROR_PTR("bytea size is invalid", __func__, NULL);
+*pw = l_getDataFourBytes(bytea, 0);
+*ph = l_getDataFourBytes(bytea, 1);
+naa = numaaCreate(n);
+for (i = 0; i < n; i++) {
+na = numaCreate(256);
+for (j = 0; j < 256; j++)
+numaAddNumber(na, bytea[8 + 256 * i + j]);
+numaaAddNuma(naa, na, L_INSERT);
+}
+return naa;
+}
+/*------------------------------------------------------------------*
+*             Translated images at the same resolution             *
+*------------------------------------------------------------------*/
+/*!
+* \brief   pixCompareWithTranslation()
+*
+* \param[in]    pix1, pix2    any depth; colormap OK
+* \param[in]    thresh        threshold for converting to 1 bpp
+* \param[out]   pdelx         x translation on pix2 to align with pix1
+* \param[out]   pdely         y translation on pix2 to align with pix1
+* \param[out]   pscore        correlation score at best alignment
+* \param[in]    debugflag     1 for debug output; 0 for no debugging
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This does a coarse-to-fine search for best translational
+*          alignment of two images, measured by a scoring function
+*          that is the correlation between the fg pixels.
+*      (2) The threshold is used if the images aren't 1 bpp.
+*      (3) With debug on, you get a pdf that shows, as a grayscale
+*          image, the score as a function of shift from the initial
+*          estimate, for each of the four levels.  The shift is 0 at
+*          the center of the image.
+*      (4) With debug on, you also get a pdf that shows the
+*          difference at the best alignment between the two images,
+*          at each of the four levels.  The red and green pixels
+*          show locations where one image has a fg pixel and the
+*          other doesn't.  The black pixels are where both images
+*          have fg pixels, and white pixels are where neither image
+*          has fg pixels.
+* </pre>
+*/
+l_ok
+pixCompareWithTranslation(PIX        *pix1,
+PIX        *pix2,
+l_int32     thresh,
+l_int32    *pdelx,
+l_int32    *pdely,
+l_float32  *pscore,
+l_int32     debugflag)
+{
+l_uint8   *subtab;
+l_int32    i, level, area1, area2, delx, dely;
+l_int32    etransx, etransy, maxshift, dbint;
+l_int32   *stab, *ctab;
+l_float32  cx1, cx2, cy1, cy2, score;
+PIX       *pixb1, *pixb2, *pixt1, *pixt2, *pixt3, *pixt4;
+PIXA      *pixa1, *pixa2, *pixadb = NULL;
+if (pdelx) *pdelx = 0;
+if (pdely) *pdely = 0;
+if (pscore) *pscore = 0.0;
+if (!pdelx || !pdely)
+return ERROR_INT("&delx and &dely not defined", __func__, 1);
+if (!pscore)
+return ERROR_INT("&score not defined", __func__, 1);
+if (!pix1)
+return ERROR_INT("pix1 not defined", __func__, 1);
+if (!pix2)
+return ERROR_INT("pix2 not defined", __func__, 1);
+/* Make tables */
+subtab = makeSubsampleTab2x();
+stab = makePixelSumTab8();
+ctab = makePixelCentroidTab8();
+/* Binarize each image */
+pixb1 = pixConvertTo1(pix1, thresh);
+pixb2 = pixConvertTo1(pix2, thresh);
+/* Make a cascade of 2x reduced images for each, thresholding
+* with level 2 (neutral), down to 8x reduction */
+pixa1 = pixaCreate(4);
+pixa2 = pixaCreate(4);
+if (debugflag)
+pixadb = pixaCreate(4);
+pixaAddPix(pixa1, pixb1, L_INSERT);
+pixaAddPix(pixa2, pixb2, L_INSERT);
+for (i = 0; i < 3; i++) {
+pixt1 = pixReduceRankBinary2(pixb1, 2, subtab);
+pixt2 = pixReduceRankBinary2(pixb2, 2, subtab);
+pixaAddPix(pixa1, pixt1, L_INSERT);
+pixaAddPix(pixa2, pixt2, L_INSERT);
+pixb1 = pixt1;
+pixb2 = pixt2;
+}
+/* At the lowest level, use the centroids with a maxshift of 6
+* to search for the best alignment.  Then at higher levels,
+* use the result from the level below as the initial approximation
+* for the alignment, and search with a maxshift of 2. */
+for (level = 3; level >= 0; level--) {
+pixt1 = pixaGetPix(pixa1, level, L_CLONE);
+pixt2 = pixaGetPix(pixa2, level, L_CLONE);
+pixCountPixels(pixt1, &area1, stab);
+pixCountPixels(pixt2, &area2, stab);
+if (level == 3) {
+pixCentroid(pixt1, ctab, stab, &cx1, &cy1);
+pixCentroid(pixt2, ctab, stab, &cx2, &cy2);
+etransx = lept_roundftoi(cx1 - cx2);
+etransy = lept_roundftoi(cy1 - cy2);
+maxshift = 6;
+} else {
+etransx = 2 * delx;
+etransy = 2 * dely;
+maxshift = 2;
+}
+dbint = (debugflag) ? level + 1 : 0;
+pixBestCorrelation(pixt1, pixt2, area1, area2, etransx, etransy,
+maxshift, stab, &delx, &dely, &score, dbint);
+if (debugflag) {
+lept_stderr("Level %d: delx = %d, dely = %d, score = %7.4f\n",
+level, delx, dely, score);
+pixRasteropIP(pixt2, delx, dely, L_BRING_IN_WHITE);
+pixt3 = pixDisplayDiffBinary(pixt1, pixt2);
+pixt4 = pixExpandReplicate(pixt3, 8 / (1 << (3 - level)));
+pixaAddPix(pixadb, pixt4, L_INSERT);
+pixDestroy(&pixt3);
+}
+pixDestroy(&pixt1);
+pixDestroy(&pixt2);
+}
+if (debugflag) {
+pixaConvertToPdf(pixadb, 300, 1.0, L_FLATE_ENCODE, 0, NULL,
+"/tmp/lept/comp/compare.pdf");
+convertFilesToPdf("/tmp/lept/comp", "correl_", 30, 1.0, L_FLATE_ENCODE,
+0, "Correlation scores at levels 1 through 5",
+"/tmp/lept/comp/correl.pdf");
+pixaDestroy(&pixadb);
+}
+*pdelx = delx;
+*pdely = dely;
+*pscore = score;
+pixaDestroy(&pixa1);
+pixaDestroy(&pixa2);
+LEPT_FREE(subtab);
+LEPT_FREE(stab);
+LEPT_FREE(ctab);
+return 0;
+}
+/*!
+* \brief   pixBestCorrelation()
+*
+* \param[in]    pix1      1 bpp
+* \param[in]    pix2      1 bpp
+* \param[in]    area1     number of on pixels in pix1
+* \param[in]    area2     number of on pixels in pix2
+* \param[in]    etransx   estimated x translation of pix2 to align with pix1
+* \param[in]    etransy   estimated y translation of pix2 to align with pix1
+* \param[in]    maxshift  max x and y shift of pix2, around the estimated
+*                         alignment location, relative to pix1
+* \param[in]    tab8      [optional] sum tab for ON pixels in byte; can be NULL
+* \param[out]   pdelx     [optional] best x shift of pix2 relative to pix1
+* \param[out]   pdely     [optional] best y shift of pix2 relative to pix1
+* \param[out]   pscore    [optional] maximum score found; can be NULL
+* \param[in]    debugflag   <= 0 to skip; positive to generate output.
+*                           The integer is used to label the debug image.
+* \return  0 if OK, 1 on error
+*
+* <pre>
+* Notes:
+*      (1) This maximizes the correlation score between two 1 bpp images,
+*          by starting with an estimate of the alignment
+*          (%etransx, %etransy) and computing the correlation around this.
+*          It optionally returns the shift (%delx, %dely) that maximizes
+*          the correlation score when pix2 is shifted by this amount
+*          relative to pix1.
+*      (2) Get the centroids of pix1 and pix2, using pixCentroid(),
+*          to compute (%etransx, %etransy).  Get the areas using
+*          pixCountPixels().
+*      (3) The centroid of pix2 is shifted with respect to the centroid
+*          of pix1 by all values between -maxshiftx and maxshiftx,
+*          and likewise for the y shifts.  Therefore, the number of
+*          correlations computed is:
+*               (2 * maxshiftx + 1) * (2 * maxshifty + 1)
+*          Consequently, if pix1 and pix2 are large, you should do this
+*          in a coarse-to-fine sequence.  See the use of this function
+*          in pixCompareWithTranslation().
+* </pre>
+*/
+l_ok
+pixBestCorrelation(PIX        *pix1,
+PIX        *pix2,
+l_int32     area1,
+l_int32     area2,
+l_int32     etransx,
+l_int32     etransy,
+l_int32     maxshift,
+l_int32    *tab8,
+l_int32    *pdelx,
+l_int32    *pdely,
+l_float32  *pscore,
+l_int32     debugflag)
+{
+l_int32    shiftx, shifty, delx, dely;
+l_int32   *tab;
+l_float32  maxscore, score;
+FPIX      *fpix = NULL;
+PIX       *pix3, *pix4;
+if (pdelx) *pdelx = 0;
+if (pdely) *pdely = 0;
+if (pscore) *pscore = 0.0;
+if (!pix1 || pixGetDepth(pix1) != 1)
+return ERROR_INT("pix1 not defined or not 1 bpp", __func__, 1);
+if (!pix2 || pixGetDepth(pix2) != 1)
+return ERROR_INT("pix2 not defined or not 1 bpp", __func__, 1);
+if (!area1 || !area2)
+return ERROR_INT("areas must be > 0", __func__, 1);
+if (debugflag > 0)
+fpix = fpixCreate(2 * maxshift + 1, 2 * maxshift + 1);
+if (!tab8)
+tab = makePixelSumTab8();
+else
+tab = tab8;
+/* Search over a set of {shiftx, shifty} for the max */
+maxscore = 0;
+delx = etransx;
+dely = etransy;
+for (shifty = -maxshift; shifty <= maxshift; shifty++) {
+for (shiftx = -maxshift; shiftx <= maxshift; shiftx++) {
+pixCorrelationScoreShifted(pix1, pix2, area1, area2,
+etransx + shiftx,
+etransy + shifty, tab, &score);
+if (debugflag > 0) {
+fpixSetPixel(fpix, maxshift + shiftx, maxshift + shifty,
+1000.0 * score);
+/*                lept_stderr("(sx, sy) = (%d, %d): score = %6.4f\n",
+shiftx, shifty, score); */
+}
+if (score > maxscore) {
+maxscore = score;
+delx = etransx + shiftx;
+dely = etransy + shifty;
+}
+}
+}
+if (debugflag > 0) {
+char  buf[128];
+lept_mkdir("lept/comp");
+pix3 = fpixDisplayMaxDynamicRange(fpix);
+pix4 = pixExpandReplicate(pix3, 20);
+snprintf(buf, sizeof(buf), "/tmp/lept/comp/correl_%d.png",
+debugflag);
+pixWrite(buf, pix4, IFF_PNG);
+pixDestroy(&pix3);
+pixDestroy(&pix4);
+fpixDestroy(&fpix);
+}
+if (pdelx) *pdelx = delx;
+if (pdely) *pdely = dely;
+if (pscore) *pscore = maxscore;
+if (!tab8) LEPT_FREE(tab);
+return 0;
+}

Mercurial > hgrepos > Python2 > PyMuPDF

comparison mupdf-source/thirdparty/leptonica/src/compare.c @ 2:b50eed0cc0ef upstream