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/media/libjpeg/jcsample.c

http://github.com/zpao/v8monkey
C | 527 lines | 305 code | 68 blank | 154 comment | 39 complexity | 4f50645b6218311abab6ef5ed93f10f8 MD5 | raw file
  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 */
 56typedef 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
 62typedef 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
 69typedef my_downsampler * my_downsample_ptr;
 70
 71
 72/*
 73 * Initialize for a downsampling pass.
 74 */
 75
 76METHODDEF(void)
 77start_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
 88LOCAL(void)
 89expand_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
115METHODDEF(void)
116sep_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
141METHODDEF(void)
142int_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
188METHODDEF(void)
189fullsize_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
213METHODDEF(void)
214h2v1_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
250METHODDEF(void)
251h2v2_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
293METHODDEF(void)
294h2v2_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
393METHODDEF(void)
394fullsize_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
465GLOBAL(void)
466jinit_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}