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comparison mupdf-source/thirdparty/libjpeg/jdsample.c @ 2:b50eed0cc0ef upstream

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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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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * jdsample.c
3 *
4 * Copyright (C) 1991-1996, Thomas G. Lane.
5 * Modified 2002-2020 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains upsampling routines.
10 *
11 * Upsampling input data is counted in "row groups". A row group
12 * is defined to be (v_samp_factor * DCT_v_scaled_size / min_DCT_v_scaled_size)
13 * sample rows of each component. Upsampling will normally produce
14 * max_v_samp_factor pixel rows from each row group (but this could vary
15 * if the upsampler is applying a scale factor of its own).
16 *
17 * An excellent reference for image resampling is
18 * Digital Image Warping, George Wolberg, 1990.
19 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
20 */
21
22 #define JPEG_INTERNALS
23 #include "jinclude.h"
24 #include "jpeglib.h"
25
26
27 /* Pointer to routine to upsample a single component */
28 typedef JMETHOD(void, upsample1_ptr,
29 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
30 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr));
31
32 /* Private subobject */
33
34 typedef struct {
35 struct jpeg_upsampler pub; /* public fields */
36
37 /* Color conversion buffer. When using separate upsampling and color
38 * conversion steps, this buffer holds one upsampled row group until it
39 * has been color converted and output.
40 * Note: we do not allocate any storage for component(s) which are full-size,
41 * ie do not need rescaling. The corresponding entry of color_buf[] is
42 * simply set to point to the input data array, thereby avoiding copying.
43 */
44 JSAMPARRAY color_buf[MAX_COMPONENTS];
45
46 /* Per-component upsampling method pointers */
47 upsample1_ptr methods[MAX_COMPONENTS];
48
49 int next_row_out; /* counts rows emitted from color_buf */
50 JDIMENSION rows_to_go; /* counts rows remaining in image */
51
52 /* Height of an input row group for each component. */
53 int rowgroup_height[MAX_COMPONENTS];
54
55 /* These arrays save pixel expansion factors so that int_expand need not
56 * recompute them each time. They are unused for other upsampling methods.
57 */
58 UINT8 h_expand[MAX_COMPONENTS];
59 UINT8 v_expand[MAX_COMPONENTS];
60 } my_upsampler;
61
62 typedef my_upsampler * my_upsample_ptr;
63
64
65 /*
66 * Initialize for an upsampling pass.
67 */
68
69 METHODDEF(void)
70 start_pass_upsample (j_decompress_ptr cinfo)
71 {
72 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
73
74 /* Mark the conversion buffer empty */
75 upsample->next_row_out = cinfo->max_v_samp_factor;
76 /* Initialize total-height counter for detecting bottom of image */
77 upsample->rows_to_go = cinfo->output_height;
78 }
79
80
81 /*
82 * Control routine to do upsampling (and color conversion).
83 *
84 * In this version we upsample each component independently.
85 * We upsample one row group into the conversion buffer, then apply
86 * color conversion a row at a time.
87 */
88
89 METHODDEF(void)
90 sep_upsample (j_decompress_ptr cinfo,
91 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
92 JDIMENSION in_row_groups_avail,
93 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
94 JDIMENSION out_rows_avail)
95 {
96 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
97 int ci;
98 jpeg_component_info * compptr;
99 JDIMENSION num_rows;
100
101 /* Fill the conversion buffer, if it's empty */
102 if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
103 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
104 ci++, compptr++) {
105 /* Don't bother to upsample an uninteresting component. */
106 if (! compptr->component_needed)
107 continue;
108 /* Invoke per-component upsample method. Notice we pass a POINTER
109 * to color_buf[ci], so that fullsize_upsample can change it.
110 */
111 (*upsample->methods[ci]) (cinfo, compptr,
112 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
113 upsample->color_buf + ci);
114 }
115 upsample->next_row_out = 0;
116 }
117
118 /* Color-convert and emit rows */
119
120 /* How many we have in the buffer: */
121 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
122 /* Not more than the distance to the end of the image. Need this test
123 * in case the image height is not a multiple of max_v_samp_factor:
124 */
125 if (num_rows > upsample->rows_to_go)
126 num_rows = upsample->rows_to_go;
127 /* And not more than what the client can accept: */
128 out_rows_avail -= *out_row_ctr;
129 if (num_rows > out_rows_avail)
130 num_rows = out_rows_avail;
131
132 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
133 (JDIMENSION) upsample->next_row_out,
134 output_buf + *out_row_ctr,
135 (int) num_rows);
136
137 /* Adjust counts */
138 *out_row_ctr += num_rows;
139 upsample->rows_to_go -= num_rows;
140 upsample->next_row_out += num_rows;
141 /* When the buffer is emptied, declare this input row group consumed */
142 if (upsample->next_row_out >= cinfo->max_v_samp_factor)
143 (*in_row_group_ctr)++;
144 }
145
146
147 /*
148 * These are the routines invoked by sep_upsample to upsample pixel values
149 * of a single component. One row group is processed per call.
150 */
151
152
153 /*
154 * For full-size components, we just make color_buf[ci] point at the
155 * input buffer, and thus avoid copying any data. Note that this is
156 * safe only because sep_upsample doesn't declare the input row group
157 * "consumed" until we are done color converting and emitting it.
158 */
159
160 METHODDEF(void)
161 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
162 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
163 {
164 *output_data_ptr = input_data;
165 }
166
167
168 /*
169 * This version handles any integral sampling ratios.
170 * This is not used for typical JPEG files, so it need not be fast.
171 * Nor, for that matter, is it particularly accurate: the algorithm is
172 * simple replication of the input pixel onto the corresponding output
173 * pixels. The hi-falutin sampling literature refers to this as a
174 * "box filter". A box filter tends to introduce visible artifacts,
175 * so if you are actually going to use 3:1 or 4:1 sampling ratios
176 * you would be well advised to improve this code.
177 */
178
179 METHODDEF(void)
180 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
181 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
182 {
183 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
184 JSAMPARRAY output_data, output_end;
185 register JSAMPROW inptr, outptr;
186 register JSAMPLE invalue;
187 register int h;
188 JSAMPROW outend;
189 int h_expand, v_expand;
190
191 h_expand = upsample->h_expand[compptr->component_index];
192 v_expand = upsample->v_expand[compptr->component_index];
193
194 output_data = *output_data_ptr;
195 output_end = output_data + cinfo->max_v_samp_factor;
196 for (; output_data < output_end; output_data += v_expand) {
197 /* Generate one output row with proper horizontal expansion */
198 inptr = *input_data++;
199 outptr = *output_data;
200 outend = outptr + cinfo->output_width;
201 while (outptr < outend) {
202 invalue = *inptr++; /* don't need GETJSAMPLE() here */
203 for (h = h_expand; h > 0; h--) {
204 *outptr++ = invalue;
205 }
206 }
207 /* Generate any additional output rows by duplicating the first one */
208 if (v_expand > 1) {
209 jcopy_sample_rows(output_data, output_data + 1,
210 v_expand - 1, cinfo->output_width);
211 }
212 }
213 }
214
215
216 /*
217 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
218 * It's still a box filter.
219 */
220
221 METHODDEF(void)
222 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
223 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
224 {
225 JSAMPARRAY output_data = *output_data_ptr;
226 register JSAMPROW inptr, outptr;
227 register JSAMPLE invalue;
228 JSAMPROW outend;
229 int outrow;
230
231 for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {
232 inptr = input_data[outrow];
233 outptr = output_data[outrow];
234 outend = outptr + cinfo->output_width;
235 while (outptr < outend) {
236 invalue = *inptr++; /* don't need GETJSAMPLE() here */
237 *outptr++ = invalue;
238 *outptr++ = invalue;
239 }
240 }
241 }
242
243
244 /*
245 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
246 * It's still a box filter.
247 */
248
249 METHODDEF(void)
250 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
251 JSAMPARRAY input_data, JSAMPIMAGE output_data_ptr)
252 {
253 JSAMPARRAY output_data, output_end;
254 register JSAMPROW inptr, outptr;
255 register JSAMPLE invalue;
256 JSAMPROW outend;
257
258 output_data = *output_data_ptr;
259 output_end = output_data + cinfo->max_v_samp_factor;
260 for (; output_data < output_end; output_data += 2) {
261 inptr = *input_data++;
262 outptr = *output_data;
263 outend = outptr + cinfo->output_width;
264 while (outptr < outend) {
265 invalue = *inptr++; /* don't need GETJSAMPLE() here */
266 *outptr++ = invalue;
267 *outptr++ = invalue;
268 }
269 jcopy_sample_rows(output_data, output_data + 1,
270 1, cinfo->output_width);
271 }
272 }
273
274
275 /*
276 * Module initialization routine for upsampling.
277 */
278
279 GLOBAL(void)
280 jinit_upsampler (j_decompress_ptr cinfo)
281 {
282 my_upsample_ptr upsample;
283 int ci;
284 jpeg_component_info * compptr;
285 int h_in_group, v_in_group, h_out_group, v_out_group;
286
287 upsample = (my_upsample_ptr) (*cinfo->mem->alloc_small)
288 ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_upsampler));
289 cinfo->upsample = &upsample->pub;
290 upsample->pub.start_pass = start_pass_upsample;
291 upsample->pub.upsample = sep_upsample;
292 upsample->pub.need_context_rows = FALSE; /* until we find out differently */
293
294 if (cinfo->CCIR601_sampling) /* this isn't supported */
295 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
296
297 /* Verify we can handle the sampling factors, select per-component methods,
298 * and create storage as needed.
299 */
300 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
301 ci++, compptr++) {
302 /* Don't bother to upsample an uninteresting component. */
303 if (! compptr->component_needed)
304 continue;
305 /* Compute size of an "input group" after IDCT scaling. This many samples
306 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
307 */
308 h_in_group = (compptr->h_samp_factor * compptr->DCT_h_scaled_size) /
309 cinfo->min_DCT_h_scaled_size;
310 v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
311 cinfo->min_DCT_v_scaled_size;
312 h_out_group = cinfo->max_h_samp_factor;
313 v_out_group = cinfo->max_v_samp_factor;
314 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
315 if (h_in_group == h_out_group && v_in_group == v_out_group) {
316 /* Fullsize components can be processed without any work. */
317 upsample->methods[ci] = fullsize_upsample;
318 continue; /* don't need to allocate buffer */
319 }
320 if (h_in_group * 2 == h_out_group && v_in_group == v_out_group) {
321 /* Special case for 2h1v upsampling */
322 upsample->methods[ci] = h2v1_upsample;
323 } else if (h_in_group * 2 == h_out_group &&
324 v_in_group * 2 == v_out_group) {
325 /* Special case for 2h2v upsampling */
326 upsample->methods[ci] = h2v2_upsample;
327 } else if ((h_out_group % h_in_group) == 0 &&
328 (v_out_group % v_in_group) == 0) {
329 /* Generic integral-factors upsampling method */
330 upsample->methods[ci] = int_upsample;
331 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
332 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
333 } else
334 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
335 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
336 ((j_common_ptr) cinfo, JPOOL_IMAGE,
337 (JDIMENSION) jround_up((long) cinfo->output_width,
338 (long) cinfo->max_h_samp_factor),
339 (JDIMENSION) cinfo->max_v_samp_factor);
340 }
341 }