--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/libjpeg/wrgif.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,566 @@
+/*
+ * wrgif.c
+ *
+ * Copyright (C) 1991-1996, Thomas G. Lane.
+ * Modified 2015-2019 by Guido Vollbeding.
+ * This file is part of the Independent JPEG Group's software.
+ * For conditions of distribution and use, see the accompanying README file.
+ *
+ * This file contains routines to write output images in GIF format.
+ *
+ * These routines may need modification for non-Unix environments or
+ * specialized applications.  As they stand, they assume output to
+ * an ordinary stdio stream.
+ */
+
+/*
+ * This code is loosely based on ppmtogif from the PBMPLUS distribution
+ * of Feb. 1991.  That file contains the following copyright notice:
+ *    Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>.
+ *    Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al.
+ *    Copyright (C) 1989 by Jef Poskanzer.
+ *    Permission to use, copy, modify, and distribute this software and its
+ *    documentation for any purpose and without fee is hereby granted, provided
+ *    that the above copyright notice appear in all copies and that both that
+ *    copyright notice and this permission notice appear in supporting
+ *    documentation.  This software is provided "as is" without express or
+ *    implied warranty.
+ */
+
+#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */
+
+#ifdef GIF_SUPPORTED
+
+
+#define	MAX_LZW_BITS	12	/* maximum LZW code size (4096 symbols) */
+
+typedef INT16 code_int;		/* must hold -1 .. 2**MAX_LZW_BITS */
+
+#define LZW_TABLE_SIZE	((code_int) 1 << MAX_LZW_BITS)
+
+#define HSIZE		5003	/* hash table size for 80% occupancy */
+
+typedef int hash_int;		/* must hold -2*HSIZE..2*HSIZE */
+
+#define MAXCODE(n_bits)	(((code_int) 1 << (n_bits)) - 1)
+
+
+/*
+ * The LZW hash table consists of two parallel arrays:
+ *   hash_code[i]	code of symbol in slot i, or 0 if empty slot
+ *   hash_value[i]	symbol's value; undefined if empty slot
+ * where slot values (i) range from 0 to HSIZE-1.  The symbol value is
+ * its prefix symbol's code concatenated with its suffix character.
+ *
+ * Algorithm:  use open addressing double hashing (no chaining) on the
+ * prefix code / suffix character combination.  We do a variant of Knuth's
+ * algorithm D (vol. 3, sec. 6.4) along with G. Knott's relatively-prime
+ * secondary probe.
+ *
+ * The hash_value[] table is allocated from FAR heap space since it would
+ * use up rather a lot of the near data space in a PC.
+ */
+
+typedef INT32 hash_entry;	/* must hold (code_int<<8) | byte */
+
+#define HASH_ENTRY(prefix, suffix)  ((((hash_entry) (prefix)) << 8) | (suffix))
+
+
+/* Private version of data destination object */
+
+typedef struct {
+  struct djpeg_dest_struct pub;	/* public fields */
+
+  j_decompress_ptr cinfo;	/* back link saves passing separate parm */
+
+  /* State for packing variable-width codes into a bitstream */
+  int n_bits;			/* current number of bits/code */
+  code_int maxcode;		/* maximum code, given n_bits */
+  int init_bits;		/* initial n_bits ... restored after clear */
+  INT32 cur_accum;		/* holds bits not yet output */
+  int cur_bits;			/* # of bits in cur_accum */
+
+  /* LZW string construction */
+  code_int waiting_code;	/* symbol not yet output; may be extendable */
+  boolean first_byte;		/* if TRUE, waiting_code is not valid */
+
+  /* State for GIF code assignment */
+  code_int ClearCode;		/* clear code (doesn't change) */
+  code_int EOFCode;		/* EOF code (ditto) */
+  code_int free_code;		/* LZW: first not-yet-used symbol code */
+  code_int code_counter;	/* not LZW: counts output symbols */
+
+  /* LZW hash table */
+  code_int *hash_code;		/* => hash table of symbol codes */
+  hash_entry FAR *hash_value;	/* => hash table of symbol values */
+
+  /* GIF data packet construction buffer */
+  int bytesinpkt;		/* # of bytes in current packet */
+  char packetbuf[256];		/* workspace for accumulating packet */
+
+} gif_dest_struct;
+
+typedef gif_dest_struct * gif_dest_ptr;
+
+
+/*
+ * Routines to package finished data bytes into GIF data blocks.
+ * A data block consists of a count byte (1..255) and that many data bytes.
+ */
+
+LOCAL(void)
+flush_packet (gif_dest_ptr dinfo)
+/* flush any accumulated data */
+{
+  if (dinfo->bytesinpkt > 0) {	/* never write zero-length packet */
+    dinfo->packetbuf[0] = (char) dinfo->bytesinpkt++;
+    if (JFWRITE(dinfo->pub.output_file, dinfo->packetbuf, dinfo->bytesinpkt)
+	!= (size_t) dinfo->bytesinpkt)
+      ERREXIT(dinfo->cinfo, JERR_FILE_WRITE);
+    dinfo->bytesinpkt = 0;
+  }
+}
+
+
+/* Add a character to current packet; flush to disk if necessary */
+#define CHAR_OUT(dinfo, c)  \
+	{ (dinfo)->packetbuf[++(dinfo)->bytesinpkt] = (char) (c);  \
+	    if ((dinfo)->bytesinpkt >= 255)  \
+	      flush_packet(dinfo);  \
+	}
+
+
+/* Routine to convert variable-width codes into a byte stream */
+
+LOCAL(void)
+output (gif_dest_ptr dinfo, code_int code)
+/* Emit a code of n_bits bits */
+/* Uses cur_accum and cur_bits to reblock into 8-bit bytes */
+{
+  dinfo->cur_accum |= ((INT32) code) << dinfo->cur_bits;
+  dinfo->cur_bits += dinfo->n_bits;
+
+  while (dinfo->cur_bits >= 8) {
+    CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
+    dinfo->cur_accum >>= 8;
+    dinfo->cur_bits -= 8;
+  }
+
+  /*
+   * If the next entry is going to be too big for the code size,
+   * then increase it, if possible.  We do this here to ensure
+   * that it's done in sync with the decoder's codesize increases.
+   */
+  if (dinfo->free_code > dinfo->maxcode) {
+    dinfo->n_bits++;
+    if (dinfo->n_bits == MAX_LZW_BITS)
+      dinfo->maxcode = LZW_TABLE_SIZE; /* free_code will never exceed this */
+    else
+      dinfo->maxcode = MAXCODE(dinfo->n_bits);
+  }
+}
+
+
+/* Compression initialization & termination */
+
+
+LOCAL(void)
+clear_hash (gif_dest_ptr dinfo)
+/* Fill the hash table with empty entries */
+{
+  /* It's sufficient to zero hash_code[] */
+  MEMZERO(dinfo->hash_code, HSIZE * SIZEOF(code_int));
+}
+
+
+LOCAL(void)
+clear_block (gif_dest_ptr dinfo)
+/* Reset compressor and issue a Clear code */
+{
+  clear_hash(dinfo);			/* delete all the symbols */
+  dinfo->free_code = dinfo->ClearCode + 2;
+  output(dinfo, dinfo->ClearCode);	/* inform decoder */
+  dinfo->n_bits = dinfo->init_bits;	/* reset code size */
+  dinfo->maxcode = MAXCODE(dinfo->n_bits);
+}
+
+
+LOCAL(void)
+compress_init (gif_dest_ptr dinfo, int i_bits)
+/* Initialize compressor */
+{
+  /* init all the state variables */
+  dinfo->n_bits = dinfo->init_bits = i_bits;
+  dinfo->maxcode = MAXCODE(dinfo->n_bits);
+  dinfo->ClearCode = ((code_int) 1 << (i_bits - 1));
+  dinfo->EOFCode = dinfo->ClearCode + 1;
+  dinfo->code_counter = dinfo->free_code = dinfo->ClearCode + 2;
+  dinfo->first_byte = TRUE;	/* no waiting symbol yet */
+  /* init output buffering vars */
+  dinfo->bytesinpkt = 0;
+  dinfo->cur_accum = 0;
+  dinfo->cur_bits = 0;
+  /* clear hash table */
+  if (dinfo->hash_code != NULL)
+    clear_hash(dinfo);
+  /* GIF specifies an initial Clear code */
+  output(dinfo, dinfo->ClearCode);
+}
+
+
+LOCAL(void)
+compress_term (gif_dest_ptr dinfo)
+/* Clean up at end */
+{
+  /* Flush out the buffered LZW code */
+  if (! dinfo->first_byte)
+    output(dinfo, dinfo->waiting_code);
+  /* Send an EOF code */
+  output(dinfo, dinfo->EOFCode);
+  /* Flush the bit-packing buffer */
+  if (dinfo->cur_bits > 0) {
+    CHAR_OUT(dinfo, dinfo->cur_accum & 0xFF);
+  }
+  /* Flush the packet buffer */
+  flush_packet(dinfo);
+}
+
+
+/* GIF header construction */
+
+
+LOCAL(void)
+put_word (gif_dest_ptr dinfo, unsigned int w)
+/* Emit a 16-bit word, LSB first */
+{
+  putc(w & 0xFF, dinfo->pub.output_file);
+  putc((w >> 8) & 0xFF, dinfo->pub.output_file);
+}
+
+
+LOCAL(void)
+put_3bytes (gif_dest_ptr dinfo, int val)
+/* Emit 3 copies of same byte value --- handy subr for colormap construction */
+{
+  putc(val, dinfo->pub.output_file);
+  putc(val, dinfo->pub.output_file);
+  putc(val, dinfo->pub.output_file);
+}
+
+
+LOCAL(void)
+emit_header (gif_dest_ptr dinfo, int num_colors, JSAMPARRAY colormap)
+/* Output the GIF file header, including color map */
+/* If colormap == NULL, synthesize a grayscale colormap */
+{
+  int BitsPerPixel, ColorMapSize, InitCodeSize, FlagByte;
+  int cshift = dinfo->cinfo->data_precision - 8;
+  int i;
+
+  if (num_colors > 256)
+    ERREXIT1(dinfo->cinfo, JERR_TOO_MANY_COLORS, num_colors);
+  /* Compute bits/pixel and related values */
+  BitsPerPixel = 1;
+  while (num_colors > (1 << BitsPerPixel))
+    BitsPerPixel++;
+  ColorMapSize = 1 << BitsPerPixel;
+  if (BitsPerPixel <= 1)
+    InitCodeSize = 2;
+  else
+    InitCodeSize = BitsPerPixel;
+  /*
+   * Write the GIF header.
+   * Note that we generate a plain GIF87 header for maximum compatibility.
+   */
+  putc('G', dinfo->pub.output_file);
+  putc('I', dinfo->pub.output_file);
+  putc('F', dinfo->pub.output_file);
+  putc('8', dinfo->pub.output_file);
+  putc('7', dinfo->pub.output_file);
+  putc('a', dinfo->pub.output_file);
+  /* Write the Logical Screen Descriptor */
+  put_word(dinfo, (unsigned int) dinfo->cinfo->output_width);
+  put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
+  FlagByte = 0x80;		/* Yes, there is a global color table */
+  FlagByte |= (BitsPerPixel - 1) << 4;	/* color resolution */
+  FlagByte |= (BitsPerPixel - 1);	/* size of global color table */
+  putc(FlagByte, dinfo->pub.output_file);
+  putc(0, dinfo->pub.output_file); /* Background color index */
+  putc(0, dinfo->pub.output_file); /* Reserved (aspect ratio in GIF89) */
+  /* Write the Global Color Map */
+  /* If the color map is more than 8 bits precision, */
+  /* we reduce it to 8 bits by shifting */
+  for (i = 0; i < ColorMapSize; i++) {
+    if (i < num_colors) {
+      if (colormap != NULL) {
+	if (dinfo->cinfo->out_color_space == JCS_RGB) {
+	  /* Normal case: RGB color map */
+	  putc(GETJSAMPLE(colormap[0][i]) >> cshift, dinfo->pub.output_file);
+	  putc(GETJSAMPLE(colormap[1][i]) >> cshift, dinfo->pub.output_file);
+	  putc(GETJSAMPLE(colormap[2][i]) >> cshift, dinfo->pub.output_file);
+	} else {
+	  /* Grayscale "color map": possible if quantizing grayscale image */
+	  put_3bytes(dinfo, GETJSAMPLE(colormap[0][i]) >> cshift);
+	}
+      } else {
+	/* Create a grayscale map of num_colors values, range 0..255 */
+	put_3bytes(dinfo, (i * 255 + (num_colors - 1) / 2) / (num_colors - 1));
+      }
+    } else {
+      /* fill out the map to a power of 2 */
+      put_3bytes(dinfo, CENTERJSAMPLE >> cshift);
+    }
+  }
+  /* Write image separator and Image Descriptor */
+  putc(',', dinfo->pub.output_file); /* separator */
+  put_word(dinfo, 0);		/* left/top offset */
+  put_word(dinfo, 0);
+  put_word(dinfo, (unsigned int) dinfo->cinfo->output_width); /* image size */
+  put_word(dinfo, (unsigned int) dinfo->cinfo->output_height);
+  /* flag byte: not interlaced, no local color map */
+  putc(0x00, dinfo->pub.output_file);
+  /* Write Initial Code Size byte */
+  putc(InitCodeSize, dinfo->pub.output_file);
+
+  /* Initialize for compression of image data */
+  compress_init(dinfo, InitCodeSize + 1);
+}
+
+
+/*
+ * Startup: write the file header.
+ */
+
+METHODDEF(void)
+start_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
+{
+  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
+
+  if (cinfo->quantize_colors)
+    emit_header(dest, cinfo->actual_number_of_colors, cinfo->colormap);
+  else
+    emit_header(dest, 256, (JSAMPARRAY) NULL);
+}
+
+
+/*
+ * Write some pixel data.
+ * In this module rows_supplied will always be 1.
+ */
+
+
+/*
+ * The LZW algorithm proper
+ */
+
+METHODDEF(void)
+put_LZW_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
+		    JDIMENSION rows_supplied)
+{
+  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
+  register JSAMPROW ptr;
+  register JDIMENSION col;
+  code_int c;
+  register hash_int i;
+  register hash_int disp;
+  register hash_entry probe_value;
+
+  ptr = dest->pub.buffer[0];
+  for (col = cinfo->output_width; col > 0; col--) {
+    /* Accept and compress one 8-bit byte */
+    c = (code_int) GETJSAMPLE(*ptr++);
+
+    if (dest->first_byte) {	/* need to initialize waiting_code */
+      dest->waiting_code = c;
+      dest->first_byte = FALSE;
+      continue;
+    }
+
+    /* Probe hash table to see if a symbol exists for
+     * waiting_code followed by c.
+     * If so, replace waiting_code by that symbol and continue.
+     */
+    i = ((hash_int) c << (MAX_LZW_BITS-8)) + dest->waiting_code;
+    /* i is less than twice 2**MAX_LZW_BITS, therefore less than twice HSIZE */
+    if (i >= HSIZE)
+      i -= HSIZE;
+
+    probe_value = HASH_ENTRY(dest->waiting_code, c);
+
+    if (dest->hash_code[i] == 0) {
+      /* hit empty slot; desired symbol not in table */
+      output(dest, dest->waiting_code);
+      if (dest->free_code < LZW_TABLE_SIZE) {
+	dest->hash_code[i] = dest->free_code++; /* add symbol to hashtable */
+	dest->hash_value[i] = probe_value;
+      } else
+	clear_block(dest);
+      dest->waiting_code = c;
+      continue;
+    }
+    if (dest->hash_value[i] == probe_value) {
+      dest->waiting_code = dest->hash_code[i];
+      continue;
+    }
+
+    if (i == 0)			/* secondary hash (after G. Knott) */
+      disp = 1;
+    else
+      disp = HSIZE - i;
+    for (;;) {
+      i -= disp;
+      if (i < 0)
+	i += HSIZE;
+      if (dest->hash_code[i] == 0) {
+	/* hit empty slot; desired symbol not in table */
+	output(dest, dest->waiting_code);
+	if (dest->free_code < LZW_TABLE_SIZE) {
+	  dest->hash_code[i] = dest->free_code++; /* add symbol to hashtable */
+	  dest->hash_value[i] = probe_value;
+	} else
+	  clear_block(dest);
+	dest->waiting_code = c;
+	break;
+      }
+      if (dest->hash_value[i] == probe_value) {
+	dest->waiting_code = dest->hash_code[i];
+	break;
+      }
+    }
+  }
+}
+
+
+/*
+ * The pseudo-compression algorithm.
+ *
+ * In this version we simply output each pixel value as a separate symbol;
+ * thus, no compression occurs.  In fact, there is expansion of one bit per
+ * pixel, because we use a symbol width one bit wider than the pixel width.
+ *
+ * GIF ordinarily uses variable-width symbols, and the decoder will expect
+ * to ratchet up the symbol width after a fixed number of symbols.
+ * To simplify the logic and keep the expansion penalty down, we emit a
+ * GIF Clear code to reset the decoder just before the width would ratchet up.
+ * Thus, all the symbols in the output file will have the same bit width.
+ * Note that emitting the Clear codes at the right times is a mere matter of
+ * counting output symbols and is in no way dependent on the LZW algorithm.
+ *
+ * With a small basic pixel width (low color count), Clear codes will be
+ * needed very frequently, causing the file to expand even more.  So this
+ * simplistic approach wouldn't work too well on bilevel images, for example.
+ * But for output of JPEG conversions the pixel width will usually be 8 bits
+ * (129 to 256 colors), so the overhead added by Clear symbols is only about
+ * one symbol in every 256.
+ */
+
+METHODDEF(void)
+put_raw_pixel_rows (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
+		    JDIMENSION rows_supplied)
+{
+  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
+  register JSAMPROW ptr;
+  register JDIMENSION col;
+  code_int c;
+
+  ptr = dest->pub.buffer[0];
+  for (col = cinfo->output_width; col > 0; col--) {
+    c = (code_int) GETJSAMPLE(*ptr++);
+    /* Accept and output one pixel value.
+     * The given value must be less than n_bits wide.
+     */
+
+    /* Output the given pixel value as a symbol. */
+    output(dest, c);
+    /* Issue Clear codes often enough to keep the reader from ratcheting up
+     * its symbol size.
+     */
+    if (dest->code_counter < dest->maxcode) {
+      dest->code_counter++;
+    } else {
+      output(dest, dest->ClearCode);
+      dest->code_counter = dest->ClearCode + 2;	/* reset the counter */
+    }
+  }
+}
+
+
+/*
+ * Finish up at the end of the file.
+ */
+
+METHODDEF(void)
+finish_output_gif (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo)
+{
+  gif_dest_ptr dest = (gif_dest_ptr) dinfo;
+
+  /* Flush compression mechanism */
+  compress_term(dest);
+  /* Write a zero-length data block to end the series */
+  putc(0, dest->pub.output_file);
+  /* Write the GIF terminator mark */
+  putc(';', dest->pub.output_file);
+  /* Make sure we wrote the output file OK */
+  JFFLUSH(dest->pub.output_file);
+  if (JFERROR(dest->pub.output_file))
+    ERREXIT(cinfo, JERR_FILE_WRITE);
+}
+
+
+/*
+ * The module selection routine for GIF format output.
+ */
+
+GLOBAL(djpeg_dest_ptr)
+jinit_write_gif (j_decompress_ptr cinfo, boolean is_lzw)
+{
+  gif_dest_ptr dest;
+
+  /* Create module interface object, fill in method pointers */
+  dest = (gif_dest_ptr) (*cinfo->mem->alloc_small)
+    ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(gif_dest_struct));
+  dest->cinfo = cinfo;		/* make back link for subroutines */
+  dest->pub.start_output = start_output_gif;
+  dest->pub.finish_output = finish_output_gif;
+
+  if (cinfo->out_color_space != JCS_GRAYSCALE &&
+      cinfo->out_color_space != JCS_RGB)
+    ERREXIT(cinfo, JERR_GIF_COLORSPACE);
+
+  /* Force quantization if color or if > 8 bits input */
+  if (cinfo->out_color_space != JCS_GRAYSCALE || cinfo->data_precision > 8) {
+    /* Force quantization to at most 256 colors */
+    cinfo->quantize_colors = TRUE;
+    if (cinfo->desired_number_of_colors > 256)
+      cinfo->desired_number_of_colors = 256;
+  }
+
+  /* Calculate output image dimensions so we can allocate space */
+  jpeg_calc_output_dimensions(cinfo);
+
+  if (cinfo->output_components != 1) /* safety check: just one component? */
+    ERREXIT(cinfo, JERR_GIF_BUG);
+
+  /* Create decompressor output buffer. */
+  dest->pub.buffer = (*cinfo->mem->alloc_sarray)
+    ((j_common_ptr) cinfo, JPOOL_IMAGE, cinfo->output_width, (JDIMENSION) 1);
+  dest->pub.buffer_height = 1;
+
+  if (is_lzw) {
+    dest->pub.put_pixel_rows = put_LZW_pixel_rows;
+    /* Allocate space for hash table */
+    dest->hash_code = (code_int *) (*cinfo->mem->alloc_small)
+      ((j_common_ptr) cinfo, JPOOL_IMAGE, HSIZE * SIZEOF(code_int));
+    dest->hash_value = (hash_entry FAR *) (*cinfo->mem->alloc_large)
+      ((j_common_ptr) cinfo, JPOOL_IMAGE, HSIZE * SIZEOF(hash_entry));
+  } else {
+    dest->pub.put_pixel_rows = put_raw_pixel_rows;
+    /* Mark tables unused */
+    dest->hash_code = NULL;
+    dest->hash_value = NULL;
+  }
+
+  return &dest->pub;
+}
+
+#endif /* GIF_SUPPORTED */