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comparison: media/libjpeg/jcsample.c

media/libjpeg/jcsample.c

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1 /*
2 * jcsample.c
3 *
4 * Copyright (C) 1991-1996, Thomas G. Lane.
5 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
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 downsampling routines.
10 *
11 * Downsampling input data is counted in "row groups". A row group
12 * is defined to be max_v_samp_factor pixel rows of each component,
13 * from which the downsampler produces v_samp_factor sample rows.
14 * A single row group is processed in each call to the downsampler module.
15 *
16 * The downsampler is responsible for edge-expansion of its output data
17 * to fill an integral number of DCT blocks horizontally. The source buffer
18 * may be modified if it is helpful for this purpose (the source buffer is
19 * allocated wide enough to correspond to the desired output width).
20 * The caller (the prep controller) is responsible for vertical padding.
21 *
22 * The downsampler may request "context rows" by setting need_context_rows
23 * during startup. In this case, the input arrays will contain at least
24 * one row group's worth of pixels above and below the passed-in data;
25 * the caller will create dummy rows at image top and bottom by replicating
26 * the first or last real pixel row.
27 *
28 * An excellent reference for image resampling is
29 * Digital Image Warping, George Wolberg, 1990.
30 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
31 *
32 * The downsampling algorithm used here is a simple average of the source
33 * pixels covered by the output pixel. The hi-falutin sampling literature
34 * refers to this as a "box filter". In general the characteristics of a box
35 * filter are not very good, but for the specific cases we normally use (1:1
36 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
37 * nearly so bad. If you intend to use other sampling ratios, you'd be well
38 * advised to improve this code.
39 *
40 * A simple input-smoothing capability is provided. This is mainly intended
41 * for cleaning up color-dithered GIF input files (if you find it inadequate,
42 * we suggest using an external filtering program such as pnmconvol). When
43 * enabled, each input pixel P is replaced by a weighted sum of itself and its
44 * eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF,
45 * where SF = (smoothing_factor / 1024).
46 * Currently, smoothing is only supported for 2h2v sampling factors.
47 */
48
49 #define JPEG_INTERNALS
50 #include "jinclude.h"
51 #include "jpeglib.h"
52 #include "jsimd.h"
53
54
55 /* Pointer to routine to downsample a single component */
56 typedef JMETHOD(void, downsample1_ptr,
57 (j_compress_ptr cinfo, jpeg_component_info * compptr,
58 JSAMPARRAY input_data, JSAMPARRAY output_data));
59
60 /* Private subobject */
61
62 typedef struct {
63 struct jpeg_downsampler pub; /* public fields */
64
65 /* Downsampling method pointers, one per component */
66 downsample1_ptr methods[MAX_COMPONENTS];
67 } my_downsampler;
68
69 typedef my_downsampler * my_downsample_ptr;
70
71
72 /*
73 * Initialize for a downsampling pass.
74 */
75
76 METHODDEF(void)
77 start_pass_downsample (j_compress_ptr cinfo)
78 {
79 /* no work for now */
80 }
81
82
83 /*
84 * Expand a component horizontally from width input_cols to width output_cols,
85 * by duplicating the rightmost samples.
86 */
87
88 LOCAL(void)
89 expand_right_edge (JSAMPARRAY image_data, int num_rows,
90 JDIMENSION input_cols, JDIMENSION output_cols)
91 {
92 register JSAMPROW ptr;
93 register JSAMPLE pixval;
94 register int count;
95 int row;
96 int numcols = (int) (output_cols - input_cols);
97
98 if (numcols > 0) {
99 for (row = 0; row < num_rows; row++) {
100 ptr = image_data[row] + input_cols;
101 pixval = ptr[-1]; /* don't need GETJSAMPLE() here */
102 for (count = numcols; count > 0; count--)
103 *ptr++ = pixval;
104 }
105 }
106 }
107
108
109 /*
110 * Do downsampling for a whole row group (all components).
111 *
112 * In this version we simply downsample each component independently.
113 */
114
115 METHODDEF(void)
116 sep_downsample (j_compress_ptr cinfo,
117 JSAMPIMAGE input_buf, JDIMENSION in_row_index,
118 JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
119 {
120 my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
121 int ci;
122 jpeg_component_info * compptr;
123 JSAMPARRAY in_ptr, out_ptr;
124
125 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
126 ci++, compptr++) {
127 in_ptr = input_buf[ci] + in_row_index;
128 out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
129 (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
130 }
131 }
132
133
134 /*
135 * Downsample pixel values of a single component.
136 * One row group is processed per call.
137 * This version handles arbitrary integral sampling ratios, without smoothing.
138 * Note that this version is not actually used for customary sampling ratios.
139 */
140
141 METHODDEF(void)
142 int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
143 JSAMPARRAY input_data, JSAMPARRAY output_data)
144 {
145 int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
146 JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */
147 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
148 JSAMPROW inptr, outptr;
149 INT32 outvalue;
150
151 h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
152 v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
153 numpix = h_expand * v_expand;
154 numpix2 = numpix/2;
155
156 /* Expand input data enough to let all the output samples be generated
157 * by the standard loop. Special-casing padded output would be more
158 * efficient.
159 */
160 expand_right_edge(input_data, cinfo->max_v_samp_factor,
161 cinfo->image_width, output_cols * h_expand);
162
163 inrow = 0;
164 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
165 outptr = output_data[outrow];
166 for (outcol = 0, outcol_h = 0; outcol < output_cols;
167 outcol++, outcol_h += h_expand) {
168 outvalue = 0;
169 for (v = 0; v < v_expand; v++) {
170 inptr = input_data[inrow+v] + outcol_h;
171 for (h = 0; h < h_expand; h++) {
172 outvalue += (INT32) GETJSAMPLE(*inptr++);
173 }
174 }
175 *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
176 }
177 inrow += v_expand;
178 }
179 }
180
181
182 /*
183 * Downsample pixel values of a single component.
184 * This version handles the special case of a full-size component,
185 * without smoothing.
186 */
187
188 METHODDEF(void)
189 fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
190 JSAMPARRAY input_data, JSAMPARRAY output_data)
191 {
192 /* Copy the data */
193 jcopy_sample_rows(input_data, 0, output_data, 0,
194 cinfo->max_v_samp_factor, cinfo->image_width);
195 /* Edge-expand */
196 expand_right_edge(output_data, cinfo->max_v_samp_factor,
197 cinfo->image_width, compptr->width_in_blocks * DCTSIZE);
198 }
199
200
201 /*
202 * Downsample pixel values of a single component.
203 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
204 * without smoothing.
205 *
206 * A note about the "bias" calculations: when rounding fractional values to
207 * integer, we do not want to always round 0.5 up to the next integer.
208 * If we did that, we'd introduce a noticeable bias towards larger values.
209 * Instead, this code is arranged so that 0.5 will be rounded up or down at
210 * alternate pixel locations (a simple ordered dither pattern).
211 */
212
213 METHODDEF(void)
214 h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
215 JSAMPARRAY input_data, JSAMPARRAY output_data)
216 {
217 int outrow;
218 JDIMENSION outcol;
219 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
220 register JSAMPROW inptr, outptr;
221 register int bias;
222
223 /* Expand input data enough to let all the output samples be generated
224 * by the standard loop. Special-casing padded output would be more
225 * efficient.
226 */
227 expand_right_edge(input_data, cinfo->max_v_samp_factor,
228 cinfo->image_width, output_cols * 2);
229
230 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
231 outptr = output_data[outrow];
232 inptr = input_data[outrow];
233 bias = 0; /* bias = 0,1,0,1,... for successive samples */
234 for (outcol = 0; outcol < output_cols; outcol++) {
235 *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
236 + bias) >> 1);
237 bias ^= 1; /* 0=>1, 1=>0 */
238 inptr += 2;
239 }
240 }
241 }
242
243
244 /*
245 * Downsample pixel values of a single component.
246 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
247 * without smoothing.
248 */
249
250 METHODDEF(void)
251 h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
252 JSAMPARRAY input_data, JSAMPARRAY output_data)
253 {
254 int inrow, outrow;
255 JDIMENSION outcol;
256 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
257 register JSAMPROW inptr0, inptr1, outptr;
258 register int bias;
259
260 /* Expand input data enough to let all the output samples be generated
261 * by the standard loop. Special-casing padded output would be more
262 * efficient.
263 */
264 expand_right_edge(input_data, cinfo->max_v_samp_factor,
265 cinfo->image_width, output_cols * 2);
266
267 inrow = 0;
268 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
269 outptr = output_data[outrow];
270 inptr0 = input_data[inrow];
271 inptr1 = input_data[inrow+1];
272 bias = 1; /* bias = 1,2,1,2,... for successive samples */
273 for (outcol = 0; outcol < output_cols; outcol++) {
274 *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
275 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
276 + bias) >> 2);
277 bias ^= 3; /* 1=>2, 2=>1 */
278 inptr0 += 2; inptr1 += 2;
279 }
280 inrow += 2;
281 }
282 }
283
284
285 #ifdef INPUT_SMOOTHING_SUPPORTED
286
287 /*
288 * Downsample pixel values of a single component.
289 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
290 * with smoothing. One row of context is required.
291 */
292
293 METHODDEF(void)
294 h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
295 JSAMPARRAY input_data, JSAMPARRAY output_data)
296 {
297 int inrow, outrow;
298 JDIMENSION colctr;
299 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
300 register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
301 INT32 membersum, neighsum, memberscale, neighscale;
302
303 /* Expand input data enough to let all the output samples be generated
304 * by the standard loop. Special-casing padded output would be more
305 * efficient.
306 */
307 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
308 cinfo->image_width, output_cols * 2);
309
310 /* We don't bother to form the individual "smoothed" input pixel values;
311 * we can directly compute the output which is the average of the four
312 * smoothed values. Each of the four member pixels contributes a fraction
313 * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
314 * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
315 * output. The four corner-adjacent neighbor pixels contribute a fraction
316 * SF to just one smoothed pixel, or SF/4 to the final output; while the
317 * eight edge-adjacent neighbors contribute SF to each of two smoothed
318 * pixels, or SF/2 overall. In order to use integer arithmetic, these
319 * factors are scaled by 2^16 = 65536.
320 * Also recall that SF = smoothing_factor / 1024.
321 */
322
323 memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
324 neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
325
326 inrow = 0;
327 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
328 outptr = output_data[outrow];
329 inptr0 = input_data[inrow];
330 inptr1 = input_data[inrow+1];
331 above_ptr = input_data[inrow-1];
332 below_ptr = input_data[inrow+2];
333
334 /* Special case for first column: pretend column -1 is same as column 0 */
335 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
336 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
337 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
338 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
339 GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
340 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
341 neighsum += neighsum;
342 neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
343 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
344 membersum = membersum * memberscale + neighsum * neighscale;
345 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
346 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
347
348 for (colctr = output_cols - 2; colctr > 0; colctr--) {
349 /* sum of pixels directly mapped to this output element */
350 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
351 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
352 /* sum of edge-neighbor pixels */
353 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
354 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
355 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
356 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
357 /* The edge-neighbors count twice as much as corner-neighbors */
358 neighsum += neighsum;
359 /* Add in the corner-neighbors */
360 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
361 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
362 /* form final output scaled up by 2^16 */
363 membersum = membersum * memberscale + neighsum * neighscale;
364 /* round, descale and output it */
365 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
366 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
367 }
368
369 /* Special case for last column */
370 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
371 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
372 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
373 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
374 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
375 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
376 neighsum += neighsum;
377 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
378 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
379 membersum = membersum * memberscale + neighsum * neighscale;
380 *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
381
382 inrow += 2;
383 }
384 }
385
386
387 /*
388 * Downsample pixel values of a single component.
389 * This version handles the special case of a full-size component,
390 * with smoothing. One row of context is required.
391 */
392
393 METHODDEF(void)
394 fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
395 JSAMPARRAY input_data, JSAMPARRAY output_data)
396 {
397 int outrow;
398 JDIMENSION colctr;
399 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
400 register JSAMPROW inptr, above_ptr, below_ptr, outptr;
401 INT32 membersum, neighsum, memberscale, neighscale;
402 int colsum, lastcolsum, nextcolsum;
403
404 /* Expand input data enough to let all the output samples be generated
405 * by the standard loop. Special-casing padded output would be more
406 * efficient.
407 */
408 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
409 cinfo->image_width, output_cols);
410
411 /* Each of the eight neighbor pixels contributes a fraction SF to the
412 * smoothed pixel, while the main pixel contributes (1-8*SF). In order
413 * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
414 * Also recall that SF = smoothing_factor / 1024.
415 */
416
417 memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
418 neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
419
420 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
421 outptr = output_data[outrow];
422 inptr = input_data[outrow];
423 above_ptr = input_data[outrow-1];
424 below_ptr = input_data[outrow+1];
425
426 /* Special case for first column */
427 colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
428 GETJSAMPLE(*inptr);
429 membersum = GETJSAMPLE(*inptr++);
430 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
431 GETJSAMPLE(*inptr);
432 neighsum = colsum + (colsum - membersum) + nextcolsum;
433 membersum = membersum * memberscale + neighsum * neighscale;
434 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
435 lastcolsum = colsum; colsum = nextcolsum;
436
437 for (colctr = output_cols - 2; colctr > 0; colctr--) {
438 membersum = GETJSAMPLE(*inptr++);
439 above_ptr++; below_ptr++;
440 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
441 GETJSAMPLE(*inptr);
442 neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
443 membersum = membersum * memberscale + neighsum * neighscale;
444 *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
445 lastcolsum = colsum; colsum = nextcolsum;
446 }
447
448 /* Special case for last column */
449 membersum = GETJSAMPLE(*inptr);
450 neighsum = lastcolsum + (colsum - membersum) + colsum;
451 membersum = membersum * memberscale + neighsum * neighscale;
452 *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
453
454 }
455 }
456
457 #endif /* INPUT_SMOOTHING_SUPPORTED */
458
459
460 /*
461 * Module initialization routine for downsampling.
462 * Note that we must select a routine for each component.
463 */
464
465 GLOBAL(void)
466 jinit_downsampler (j_compress_ptr cinfo)
467 {
468 my_downsample_ptr downsample;
469 int ci;
470 jpeg_component_info * compptr;
471 boolean smoothok = TRUE;
472
473 downsample = (my_downsample_ptr)
474 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
475 SIZEOF(my_downsampler));
476 cinfo->downsample = (struct jpeg_downsampler *) downsample;
477 downsample->pub.start_pass = start_pass_downsample;
478 downsample->pub.downsample = sep_downsample;
479 downsample->pub.need_context_rows = FALSE;
480
481 if (cinfo->CCIR601_sampling)
482 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
483
484 /* Verify we can handle the sampling factors, and set up method pointers */
485 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
486 ci++, compptr++) {
487 if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
488 compptr->v_samp_factor == cinfo->max_v_samp_factor) {
489 #ifdef INPUT_SMOOTHING_SUPPORTED
490 if (cinfo->smoothing_factor) {
491 downsample->methods[ci] = fullsize_smooth_downsample;
492 downsample->pub.need_context_rows = TRUE;
493 } else
494 #endif
495 downsample->methods[ci] = fullsize_downsample;
496 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
497 compptr->v_samp_factor == cinfo->max_v_samp_factor) {
498 smoothok = FALSE;
499 if (jsimd_can_h2v1_downsample())
500 downsample->methods[ci] = jsimd_h2v1_downsample;
501 else
502 downsample->methods[ci] = h2v1_downsample;
503 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
504 compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
505 #ifdef INPUT_SMOOTHING_SUPPORTED
506 if (cinfo->smoothing_factor) {
507 downsample->methods[ci] = h2v2_smooth_downsample;
508 downsample->pub.need_context_rows = TRUE;
509 } else
510 #endif
511 if (jsimd_can_h2v2_downsample())
512 downsample->methods[ci] = jsimd_h2v2_downsample;
513 else
514 downsample->methods[ci] = h2v2_downsample;
515 } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
516 (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
517 smoothok = FALSE;
518 downsample->methods[ci] = int_downsample;
519 } else
520 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
521 }
522
523 #ifdef INPUT_SMOOTHING_SUPPORTED
524 if (cinfo->smoothing_factor && !smoothok)
525 TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
526 #endif
527 }

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