1/*
2 * jcsample.c
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1991-1996, Thomas G. Lane.
6 * libjpeg-turbo Modifications:
7 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
8 * Copyright (C) 2014, MIPS Technologies, Inc., California.
9 * Copyright (C) 2015, D. R. Commander.
10 * For conditions of distribution and use, see the accompanying README.ijg
11 * file.
12 *
13 * This file contains downsampling routines.
14 *
15 * Downsampling input data is counted in "row groups". A row group
16 * is defined to be max_v_samp_factor pixel rows of each component,
17 * from which the downsampler produces v_samp_factor sample rows.
18 * A single row group is processed in each call to the downsampler module.
19 *
20 * The downsampler is responsible for edge-expansion of its output data
21 * to fill an integral number of DCT blocks horizontally. The source buffer
22 * may be modified if it is helpful for this purpose (the source buffer is
23 * allocated wide enough to correspond to the desired output width).
24 * The caller (the prep controller) is responsible for vertical padding.
25 *
26 * The downsampler may request "context rows" by setting need_context_rows
27 * during startup. In this case, the input arrays will contain at least
28 * one row group's worth of pixels above and below the passed-in data;
29 * the caller will create dummy rows at image top and bottom by replicating
30 * the first or last real pixel row.
31 *
32 * An excellent reference for image resampling is
33 * Digital Image Warping, George Wolberg, 1990.
34 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
35 *
36 * The downsampling algorithm used here is a simple average of the source
37 * pixels covered by the output pixel. The hi-falutin sampling literature
38 * refers to this as a "box filter". In general the characteristics of a box
39 * filter are not very good, but for the specific cases we normally use (1:1
40 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
41 * nearly so bad. If you intend to use other sampling ratios, you'd be well
42 * advised to improve this code.
43 *
44 * A simple input-smoothing capability is provided. This is mainly intended
45 * for cleaning up color-dithered GIF input files (if you find it inadequate,
46 * we suggest using an external filtering program such as pnmconvol). When
47 * enabled, each input pixel P is replaced by a weighted sum of itself and its
48 * eight neighbors. P's weight is 1-8*SF and each neighbor's weight is SF,
49 * where SF = (smoothing_factor / 1024).
50 * Currently, smoothing is only supported for 2h2v sampling factors.
51 */
52
53#define JPEG_INTERNALS
54#include "jinclude.h"
55#include "jpeglib.h"
56#include "jsimd.h"
57
58
59/* Pointer to routine to downsample a single component */
60typedef void (*downsample1_ptr) (j_compress_ptr cinfo,
61 jpeg_component_info *compptr,
62 JSAMPARRAY input_data,
63 JSAMPARRAY output_data);
64
65/* Private subobject */
66
67typedef struct {
68 struct jpeg_downsampler pub; /* public fields */
69
70 /* Downsampling method pointers, one per component */
71 downsample1_ptr methods[MAX_COMPONENTS];
72} my_downsampler;
73
74typedef my_downsampler *my_downsample_ptr;
75
76
77/*
78 * Initialize for a downsampling pass.
79 */
80
81METHODDEF(void)
82start_pass_downsample(j_compress_ptr cinfo)
83{
84 /* no work for now */
85}
86
87
88/*
89 * Expand a component horizontally from width input_cols to width output_cols,
90 * by duplicating the rightmost samples.
91 */
92
93LOCAL(void)
94expand_right_edge(JSAMPARRAY image_data, int num_rows, JDIMENSION input_cols,
95 JDIMENSION output_cols)
96{
97 register JSAMPROW ptr;
98 register JSAMPLE pixval;
99 register int count;
100 int row;
101 int numcols = (int)(output_cols - input_cols);
102
103 if (numcols > 0) {
104 for (row = 0; row < num_rows; row++) {
105 ptr = image_data[row] + input_cols;
106 pixval = ptr[-1]; /* don't need GETJSAMPLE() here */
107 for (count = numcols; count > 0; count--)
108 *ptr++ = pixval;
109 }
110 }
111}
112
113
114/*
115 * Do downsampling for a whole row group (all components).
116 *
117 * In this version we simply downsample each component independently.
118 */
119
120METHODDEF(void)
121sep_downsample(j_compress_ptr cinfo, JSAMPIMAGE input_buf,
122 JDIMENSION in_row_index, JSAMPIMAGE output_buf,
123 JDIMENSION out_row_group_index)
124{
125 my_downsample_ptr downsample = (my_downsample_ptr)cinfo->downsample;
126 int ci;
127 jpeg_component_info *compptr;
128 JSAMPARRAY in_ptr, out_ptr;
129
130 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
131 ci++, compptr++) {
132 in_ptr = input_buf[ci] + in_row_index;
133 out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
134 (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
135 }
136}
137
138
139/*
140 * Downsample pixel values of a single component.
141 * One row group is processed per call.
142 * This version handles arbitrary integral sampling ratios, without smoothing.
143 * Note that this version is not actually used for customary sampling ratios.
144 */
145
146METHODDEF(void)
147int_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
148 JSAMPARRAY input_data, JSAMPARRAY output_data)
149{
150 int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
151 JDIMENSION outcol, outcol_h; /* outcol_h == outcol*h_expand */
152 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
153 JSAMPROW inptr, outptr;
154 JLONG outvalue;
155
156 h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
157 v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
158 numpix = h_expand * v_expand;
159 numpix2 = numpix / 2;
160
161 /* Expand input data enough to let all the output samples be generated
162 * by the standard loop. Special-casing padded output would be more
163 * efficient.
164 */
165 expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,
166 output_cols * h_expand);
167
168 inrow = 0;
169 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
170 outptr = output_data[outrow];
171 for (outcol = 0, outcol_h = 0; outcol < output_cols;
172 outcol++, outcol_h += h_expand) {
173 outvalue = 0;
174 for (v = 0; v < v_expand; v++) {
175 inptr = input_data[inrow + v] + outcol_h;
176 for (h = 0; h < h_expand; h++) {
177 outvalue += (JLONG)GETJSAMPLE(*inptr++);
178 }
179 }
180 *outptr++ = (JSAMPLE)((outvalue + numpix2) / numpix);
181 }
182 inrow += v_expand;
183 }
184}
185
186
187/*
188 * Downsample pixel values of a single component.
189 * This version handles the special case of a full-size component,
190 * without smoothing.
191 */
192
193METHODDEF(void)
194fullsize_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
195 JSAMPARRAY input_data, JSAMPARRAY output_data)
196{
197 /* Copy the data */
198 jcopy_sample_rows(input_data, 0, output_data, 0, cinfo->max_v_samp_factor,
199 cinfo->image_width);
200 /* Edge-expand */
201 expand_right_edge(output_data, cinfo->max_v_samp_factor, cinfo->image_width,
202 compptr->width_in_blocks * DCTSIZE);
203}
204
205
206/*
207 * Downsample pixel values of a single component.
208 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
209 * without smoothing.
210 *
211 * A note about the "bias" calculations: when rounding fractional values to
212 * integer, we do not want to always round 0.5 up to the next integer.
213 * If we did that, we'd introduce a noticeable bias towards larger values.
214 * Instead, this code is arranged so that 0.5 will be rounded up or down at
215 * alternate pixel locations (a simple ordered dither pattern).
216 */
217
218METHODDEF(void)
219h2v1_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
220 JSAMPARRAY input_data, JSAMPARRAY output_data)
221{
222 int outrow;
223 JDIMENSION outcol;
224 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
225 register JSAMPROW inptr, outptr;
226 register int bias;
227
228 /* Expand input data enough to let all the output samples be generated
229 * by the standard loop. Special-casing padded output would be more
230 * efficient.
231 */
232 expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,
233 output_cols * 2);
234
235 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
236 outptr = output_data[outrow];
237 inptr = input_data[outrow];
238 bias = 0; /* bias = 0,1,0,1,... for successive samples */
239 for (outcol = 0; outcol < output_cols; outcol++) {
240 *outptr++ =
241 (JSAMPLE)((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1]) + bias) >> 1);
242 bias ^= 1; /* 0=>1, 1=>0 */
243 inptr += 2;
244 }
245 }
246}
247
248
249/*
250 * Downsample pixel values of a single component.
251 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
252 * without smoothing.
253 */
254
255METHODDEF(void)
256h2v2_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
257 JSAMPARRAY input_data, JSAMPARRAY output_data)
258{
259 int inrow, outrow;
260 JDIMENSION outcol;
261 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
262 register JSAMPROW inptr0, inptr1, outptr;
263 register int bias;
264
265 /* Expand input data enough to let all the output samples be generated
266 * by the standard loop. Special-casing padded output would be more
267 * efficient.
268 */
269 expand_right_edge(input_data, cinfo->max_v_samp_factor, cinfo->image_width,
270 output_cols * 2);
271
272 inrow = 0;
273 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
274 outptr = output_data[outrow];
275 inptr0 = input_data[inrow];
276 inptr1 = input_data[inrow + 1];
277 bias = 1; /* bias = 1,2,1,2,... for successive samples */
278 for (outcol = 0; outcol < output_cols; outcol++) {
279 *outptr++ =
280 (JSAMPLE)((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
281 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]) + bias) >> 2);
282 bias ^= 3; /* 1=>2, 2=>1 */
283 inptr0 += 2; inptr1 += 2;
284 }
285 inrow += 2;
286 }
287}
288
289
290#ifdef INPUT_SMOOTHING_SUPPORTED
291
292/*
293 * Downsample pixel values of a single component.
294 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
295 * with smoothing. One row of context is required.
296 */
297
298METHODDEF(void)
299h2v2_smooth_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
300 JSAMPARRAY input_data, JSAMPARRAY output_data)
301{
302 int inrow, outrow;
303 JDIMENSION colctr;
304 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
305 register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
306 JLONG membersum, neighsum, memberscale, neighscale;
307
308 /* Expand input data enough to let all the output samples be generated
309 * by the standard loop. Special-casing padded output would be more
310 * efficient.
311 */
312 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
313 cinfo->image_width, output_cols * 2);
314
315 /* We don't bother to form the individual "smoothed" input pixel values;
316 * we can directly compute the output which is the average of the four
317 * smoothed values. Each of the four member pixels contributes a fraction
318 * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
319 * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
320 * output. The four corner-adjacent neighbor pixels contribute a fraction
321 * SF to just one smoothed pixel, or SF/4 to the final output; while the
322 * eight edge-adjacent neighbors contribute SF to each of two smoothed
323 * pixels, or SF/2 overall. In order to use integer arithmetic, these
324 * factors are scaled by 2^16 = 65536.
325 * Also recall that SF = smoothing_factor / 1024.
326 */
327
328 memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
329 neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
330
331 inrow = 0;
332 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
333 outptr = output_data[outrow];
334 inptr0 = input_data[inrow];
335 inptr1 = input_data[inrow + 1];
336 above_ptr = input_data[inrow - 1];
337 below_ptr = input_data[inrow + 2];
338
339 /* Special case for first column: pretend column -1 is same as column 0 */
340 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
341 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
342 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
343 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
344 GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
345 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
346 neighsum += neighsum;
347 neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
348 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
349 membersum = membersum * memberscale + neighsum * neighscale;
350 *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
351 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
352
353 for (colctr = output_cols - 2; colctr > 0; colctr--) {
354 /* sum of pixels directly mapped to this output element */
355 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
356 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
357 /* sum of edge-neighbor pixels */
358 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
359 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
360 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
361 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
362 /* The edge-neighbors count twice as much as corner-neighbors */
363 neighsum += neighsum;
364 /* Add in the corner-neighbors */
365 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
366 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
367 /* form final output scaled up by 2^16 */
368 membersum = membersum * memberscale + neighsum * neighscale;
369 /* round, descale and output it */
370 *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
371 inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
372 }
373
374 /* Special case for last column */
375 membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
376 GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
377 neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
378 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
379 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
380 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
381 neighsum += neighsum;
382 neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
383 GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
384 membersum = membersum * memberscale + neighsum * neighscale;
385 *outptr = (JSAMPLE)((membersum + 32768) >> 16);
386
387 inrow += 2;
388 }
389}
390
391
392/*
393 * Downsample pixel values of a single component.
394 * This version handles the special case of a full-size component,
395 * with smoothing. One row of context is required.
396 */
397
398METHODDEF(void)
399fullsize_smooth_downsample(j_compress_ptr cinfo, jpeg_component_info *compptr,
400 JSAMPARRAY input_data, JSAMPARRAY output_data)
401{
402 int outrow;
403 JDIMENSION colctr;
404 JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
405 register JSAMPROW inptr, above_ptr, below_ptr, outptr;
406 JLONG membersum, neighsum, memberscale, neighscale;
407 int colsum, lastcolsum, nextcolsum;
408
409 /* Expand input data enough to let all the output samples be generated
410 * by the standard loop. Special-casing padded output would be more
411 * efficient.
412 */
413 expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
414 cinfo->image_width, output_cols);
415
416 /* Each of the eight neighbor pixels contributes a fraction SF to the
417 * smoothed pixel, while the main pixel contributes (1-8*SF). In order
418 * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
419 * Also recall that SF = smoothing_factor / 1024.
420 */
421
422 memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
423 neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
424
425 for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
426 outptr = output_data[outrow];
427 inptr = input_data[outrow];
428 above_ptr = input_data[outrow - 1];
429 below_ptr = input_data[outrow + 1];
430
431 /* Special case for first column */
432 colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
433 GETJSAMPLE(*inptr);
434 membersum = GETJSAMPLE(*inptr++);
435 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
436 GETJSAMPLE(*inptr);
437 neighsum = colsum + (colsum - membersum) + nextcolsum;
438 membersum = membersum * memberscale + neighsum * neighscale;
439 *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
440 lastcolsum = colsum; colsum = nextcolsum;
441
442 for (colctr = output_cols - 2; colctr > 0; colctr--) {
443 membersum = GETJSAMPLE(*inptr++);
444 above_ptr++; below_ptr++;
445 nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
446 GETJSAMPLE(*inptr);
447 neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
448 membersum = membersum * memberscale + neighsum * neighscale;
449 *outptr++ = (JSAMPLE)((membersum + 32768) >> 16);
450 lastcolsum = colsum; colsum = nextcolsum;
451 }
452
453 /* Special case for last column */
454 membersum = GETJSAMPLE(*inptr);
455 neighsum = lastcolsum + (colsum - membersum) + colsum;
456 membersum = membersum * memberscale + neighsum * neighscale;
457 *outptr = (JSAMPLE)((membersum + 32768) >> 16);
458
459 }
460}
461
462#endif /* INPUT_SMOOTHING_SUPPORTED */
463
464
465/*
466 * Module initialization routine for downsampling.
467 * Note that we must select a routine for each component.
468 */
469
470GLOBAL(void)
471jinit_downsampler(j_compress_ptr cinfo)
472{
473 my_downsample_ptr downsample;
474 int ci;
475 jpeg_component_info *compptr;
476 boolean smoothok = TRUE;
477
478 downsample = (my_downsample_ptr)
479 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
480 sizeof(my_downsampler));
481 cinfo->downsample = (struct jpeg_downsampler *)downsample;
482 downsample->pub.start_pass = start_pass_downsample;
483 downsample->pub.downsample = sep_downsample;
484 downsample->pub.need_context_rows = FALSE;
485
486 if (cinfo->CCIR601_sampling)
487 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
488
489 /* Verify we can handle the sampling factors, and set up method pointers */
490 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
491 ci++, compptr++) {
492 if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
493 compptr->v_samp_factor == cinfo->max_v_samp_factor) {
494#ifdef INPUT_SMOOTHING_SUPPORTED
495 if (cinfo->smoothing_factor) {
496 downsample->methods[ci] = fullsize_smooth_downsample;
497 downsample->pub.need_context_rows = TRUE;
498 } else
499#endif
500 downsample->methods[ci] = fullsize_downsample;
501 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
502 compptr->v_samp_factor == cinfo->max_v_samp_factor) {
503 smoothok = FALSE;
504 if (jsimd_can_h2v1_downsample())
505 downsample->methods[ci] = jsimd_h2v1_downsample;
506 else
507 downsample->methods[ci] = h2v1_downsample;
508 } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
509 compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
510#ifdef INPUT_SMOOTHING_SUPPORTED
511 if (cinfo->smoothing_factor) {
512#if defined(__mips__)
513 if (jsimd_can_h2v2_smooth_downsample())
514 downsample->methods[ci] = jsimd_h2v2_smooth_downsample;
515 else
516#endif
517 downsample->methods[ci] = h2v2_smooth_downsample;
518 downsample->pub.need_context_rows = TRUE;
519 } else
520#endif
521 {
522 if (jsimd_can_h2v2_downsample())
523 downsample->methods[ci] = jsimd_h2v2_downsample;
524 else
525 downsample->methods[ci] = h2v2_downsample;
526 }
527 } else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
528 (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
529 smoothok = FALSE;
530 downsample->methods[ci] = int_downsample;
531 } else
532 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
533 }
534
535#ifdef INPUT_SMOOTHING_SUPPORTED
536 if (cinfo->smoothing_factor && !smoothok)
537 TRACEMS(cinfo, 0, JTRC_SMOOTH_NOTIMPL);
538#endif
539}
540