source: golgotha/src/i4/loaders/jpg/jcsample.cc @ 80

Last change on this file since 80 was 80, checked in by Sam Hocevar, 11 years ago
  • Adding the Golgotha source code. Not sure what's going to be interesting in there, but since it's all public domain, there's certainly stuff to pick up.
File size: 19.4 KB
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1/********************************************************************** <BR>
2  This file is part of Crack dot Com's free source code release of
3  Golgotha. <a href="http://www.crack.com/golgotha_release"> <BR> for
4  information about compiling & licensing issues visit this URL</a>
5  <PRE> If that doesn't help, contact Jonathan Clark at
6  golgotha_source@usa.net (Subject should have "GOLG" in it)
7***********************************************************************/
8
9/*
10 * jcsample.c
11 *
12 * Copyright (C) 1991-1996, Thomas G. Lane.
13 * This file is part of the Independent JPEG Group's software.
14 * For conditions of distribution and use, see the accompanying README file.
15 *
16 * This file contains downsampling routines.
17 *
18 * Downsampling input data is counted in "row groups".  A row group
19 * is defined to be max_v_samp_factor pixel rows of each component,
20 * from which the downsampler produces v_samp_factor sample rows.
21 * A single row group is processed in each call to the downsampler module.
22 *
23 * The downsampler is responsible for edge-expansion of its output data
24 * to fill an integral number of DCT blocks horizontally.  The source buffer
25 * may be modified if it is helpful for this purpose (the source buffer is
26 * allocated wide enough to correspond to the desired output width).
27 * The caller (the prep controller) is responsible for vertical padding.
28 *
29 * The downsampler may request "context rows" by setting need_context_rows
30 * during startup.  In this case, the input arrays will contain at least
31 * one row group's worth of pixels above and below the passed-in data;
32 * the caller will create dummy rows at image top and bottom by replicating
33 * the first or last real pixel row.
34 *
35 * An excellent reference for image resampling is
36 *   Digital Image Warping, George Wolberg, 1990.
37 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
38 *
39 * The downsampling algorithm used here is a simple average of the source
40 * pixels covered by the output pixel.  The hi-falutin sampling literature
41 * refers to this as a "box filter".  In general the characteristics of a box
42 * filter are not very good, but for the specific cases we normally use (1:1
43 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
44 * nearly so bad.  If you intend to use other sampling ratios, you'd be well
45 * advised to improve this code.
46 *
47 * A simple input-smoothing capability is provided.  This is mainly intended
48 * for cleaning up color-dithered GIF input files (if you find it inadequate,
49 * we suggest using an external filtering program such as pnmconvol).  When
50 * enabled, each input pixel P is replaced by a weighted sum of itself and its
51 * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,
52 * where SF = (smoothing_factor / 1024).
53 * Currently, smoothing is only supported for 2h2v sampling factors.
54 */
55
56#define JPEG_INTERNALS
57#include "loaders/jpg/jinclude.h"
58#include "loaders/jpg/jpeglib.h"
59
60
61/* Pointer to routine to downsample a single component */
62typedef JMETHOD(void, downsample1_ptr,
63                (j_compress_ptr cinfo, jpeg_component_info * compptr,
64                 JSAMPARRAY input_data, JSAMPARRAY output_data));
65
66/* Private subobject */
67
68typedef struct {
69  struct jpeg_downsampler pub;  /* public fields */
70
71  /* Downsampling method pointers, one per component */
72  downsample1_ptr methods[MAX_COMPONENTS];
73} my_downsampler;
74
75typedef my_downsampler * my_downsample_ptr;
76
77
78/*
79 * Initialize for a downsampling pass.
80 */
81
82METHODDEF(void)
83start_pass_downsample (j_compress_ptr cinfo)
84{
85  /* no work for now */
86}
87
88
89/*
90 * Expand a component horizontally from width input_cols to width output_cols,
91 * by duplicating the rightmost samples.
92 */
93
94LOCAL(void)
95expand_right_edge (JSAMPARRAY image_data, int num_rows,
96                   JDIMENSION input_cols, JDIMENSION output_cols)
97{
98  register JSAMPROW ptr;
99  register JSAMPLE pixval;
100  register int count;
101  int row;
102  int numcols = (int) (output_cols - input_cols);
103
104  if (numcols > 0) {
105    for (row = 0; row < num_rows; row++) {
106      ptr = image_data[row] + input_cols;
107      pixval = ptr[-1];         /* don't need GETJSAMPLE() here */
108      for (count = numcols; count > 0; count--)
109        *ptr++ = pixval;
110    }
111  }
112}
113
114
115/*
116 * Do downsampling for a whole row group (all components).
117 *
118 * In this version we simply downsample each component independently.
119 */
120
121METHODDEF(void)
122sep_downsample (j_compress_ptr cinfo,
123                JSAMPIMAGE input_buf, JDIMENSION in_row_index,
124                JSAMPIMAGE output_buf, JDIMENSION out_row_group_index)
125{
126  my_downsample_ptr downsample = (my_downsample_ptr) cinfo->downsample;
127  int ci;
128  jpeg_component_info * compptr;
129  JSAMPARRAY in_ptr, out_ptr;
130
131  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
132       ci++, compptr++) {
133    in_ptr = input_buf[ci] + in_row_index;
134    out_ptr = output_buf[ci] + (out_row_group_index * compptr->v_samp_factor);
135    (*downsample->methods[ci]) (cinfo, compptr, in_ptr, out_ptr);
136  }
137}
138
139
140/*
141 * Downsample pixel values of a single component.
142 * One row group is processed per call.
143 * This version handles arbitrary integral sampling ratios, without smoothing.
144 * Note that this version is not actually used for customary sampling ratios.
145 */
146
147METHODDEF(void)
148int_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
149                JSAMPARRAY input_data, JSAMPARRAY output_data)
150{
151  int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
152  JDIMENSION outcol, outcol_h;  /* outcol_h == outcol*h_expand */
153  JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
154  JSAMPROW inptr, outptr;
155  INT32 outvalue;
156
157  h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
158  v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
159  numpix = h_expand * v_expand;
160  numpix2 = numpix/2;
161
162  /* Expand input data enough to let all the output samples be generated
163   * by the standard loop.  Special-casing padded output would be more
164   * efficient.
165   */
166  expand_right_edge(input_data, cinfo->max_v_samp_factor,
167                    cinfo->image_width, output_cols * h_expand);
168
169  inrow = 0;
170  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
171    outptr = output_data[outrow];
172    for (outcol = 0, outcol_h = 0; outcol < output_cols;
173         outcol++, outcol_h += h_expand) {
174      outvalue = 0;
175      for (v = 0; v < v_expand; v++) {
176        inptr = input_data[inrow+v] + outcol_h;
177        for (h = 0; h < h_expand; h++) {
178          outvalue += (INT32) GETJSAMPLE(*inptr++);
179        }
180      }
181      *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
182    }
183    inrow += v_expand;
184  }
185}
186
187
188/*
189 * Downsample pixel values of a single component.
190 * This version handles the special case of a full-size component,
191 * without smoothing.
192 */
193
194METHODDEF(void)
195fullsize_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
196                     JSAMPARRAY input_data, JSAMPARRAY output_data)
197{
198  /* Copy the data */
199  jcopy_sample_rows(input_data, 0, output_data, 0,
200                    cinfo->max_v_samp_factor, cinfo->image_width);
201  /* Edge-expand */
202  expand_right_edge(output_data, cinfo->max_v_samp_factor,
203                    cinfo->image_width, compptr->width_in_blocks * DCTSIZE);
204}
205
206
207/*
208 * Downsample pixel values of a single component.
209 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
210 * without smoothing.
211 *
212 * A note about the "bias" calculations: when rounding fractional values to
213 * integer, we do not want to always round 0.5 up to the next integer.
214 * If we did that, we'd introduce a noticeable bias towards larger values.
215 * Instead, this code is arranged so that 0.5 will be rounded up or down at
216 * alternate pixel locations (a simple ordered dither pattern).
217 */
218
219METHODDEF(void)
220h2v1_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
221                 JSAMPARRAY input_data, JSAMPARRAY output_data)
222{
223  int outrow;
224  JDIMENSION outcol;
225  JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
226  register JSAMPROW inptr, outptr;
227  register int bias;
228
229  /* Expand input data enough to let all the output samples be generated
230   * by the standard loop.  Special-casing padded output would be more
231   * efficient.
232   */
233  expand_right_edge(input_data, cinfo->max_v_samp_factor,
234                    cinfo->image_width, output_cols * 2);
235
236  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
237    outptr = output_data[outrow];
238    inptr = input_data[outrow];
239    bias = 0;                   /* bias = 0,1,0,1,... for successive samples */
240    for (outcol = 0; outcol < output_cols; outcol++) {
241      *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
242                              + bias) >> 1);
243      bias ^= 1;                /* 0=>1, 1=>0 */
244      inptr += 2;
245    }
246  }
247}
248
249
250/*
251 * Downsample pixel values of a single component.
252 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
253 * without smoothing.
254 */
255
256METHODDEF(void)
257h2v2_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
258                 JSAMPARRAY input_data, JSAMPARRAY output_data)
259{
260  int inrow, outrow;
261  JDIMENSION outcol;
262  JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
263  register JSAMPROW inptr0, inptr1, outptr;
264  register int bias;
265
266  /* Expand input data enough to let all the output samples be generated
267   * by the standard loop.  Special-casing padded output would be more
268   * efficient.
269   */
270  expand_right_edge(input_data, cinfo->max_v_samp_factor,
271                    cinfo->image_width, output_cols * 2);
272
273  inrow = 0;
274  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
275    outptr = output_data[outrow];
276    inptr0 = input_data[inrow];
277    inptr1 = input_data[inrow+1];
278    bias = 1;                   /* bias = 1,2,1,2,... for successive samples */
279    for (outcol = 0; outcol < output_cols; outcol++) {
280      *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
281                              GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
282                              + bias) >> 2);
283      bias ^= 3;                /* 1=>2, 2=>1 */
284      inptr0 += 2; inptr1 += 2;
285    }
286    inrow += 2;
287  }
288}
289
290
291#ifdef INPUT_SMOOTHING_SUPPORTED
292
293/*
294 * Downsample pixel values of a single component.
295 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
296 * with smoothing.  One row of context is required.
297 */
298
299METHODDEF(void)
300h2v2_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info * compptr,
301                        JSAMPARRAY input_data, JSAMPARRAY output_data)
302{
303  int inrow, outrow;
304  JDIMENSION colctr;
305  JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
306  register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
307  INT32 membersum, neighsum, memberscale, neighscale;
308
309  /* Expand input data enough to let all the output samples be generated
310   * by the standard loop.  Special-casing padded output would be more
311   * efficient.
312   */
313  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
314                    cinfo->image_width, output_cols * 2);
315
316  /* We don't bother to form the individual "smoothed" input pixel values;
317   * we can directly compute the output which is the average of the four
318   * smoothed values.  Each of the four member pixels contributes a fraction
319   * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
320   * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
321   * output.  The four corner-adjacent neighbor pixels contribute a fraction
322   * SF to just one smoothed pixel, or SF/4 to the final output; while the
323   * eight edge-adjacent neighbors contribute SF to each of two smoothed
324   * pixels, or SF/2 overall.  In order to use integer arithmetic, these
325   * factors are scaled by 2^16 = 65536.
326   * Also recall that SF = smoothing_factor / 1024.
327   */
328
329  memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
330  neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */
331
332  inrow = 0;
333  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
334    outptr = output_data[outrow];
335    inptr0 = input_data[inrow];
336    inptr1 = input_data[inrow+1];
337    above_ptr = input_data[inrow-1];
338    below_ptr = input_data[inrow+2];
339
340    /* Special case for first column: pretend column -1 is same as column 0 */
341    membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
342                GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
343    neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
344               GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
345               GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
346               GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
347    neighsum += neighsum;
348    neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
349                GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
350    membersum = membersum * memberscale + neighsum * neighscale;
351    *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
352    inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
353
354    for (colctr = output_cols - 2; colctr > 0; colctr--) {
355      /* sum of pixels directly mapped to this output element */
356      membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
357                  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
358      /* sum of edge-neighbor pixels */
359      neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
360                 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
361                 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
362                 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
363      /* The edge-neighbors count twice as much as corner-neighbors */
364      neighsum += neighsum;
365      /* Add in the corner-neighbors */
366      neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
367                  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
368      /* form final output scaled up by 2^16 */
369      membersum = membersum * memberscale + neighsum * neighscale;
370      /* round, descale and output it */
371      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
372      inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
373    }
374
375    /* Special case for last column */
376    membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
377                GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
378    neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
379               GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
380               GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
381               GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
382    neighsum += neighsum;
383    neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
384                GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
385    membersum = membersum * memberscale + neighsum * neighscale;
386    *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
387
388    inrow += 2;
389  }
390}
391
392
393/*
394 * Downsample pixel values of a single component.
395 * This version handles the special case of a full-size component,
396 * with smoothing.  One row of context is required.
397 */
398
399METHODDEF(void)
400fullsize_smooth_downsample (j_compress_ptr cinfo, jpeg_component_info *compptr,
401                            JSAMPARRAY input_data, JSAMPARRAY output_data)
402{
403  int outrow;
404  JDIMENSION colctr;
405  JDIMENSION output_cols = compptr->width_in_blocks * DCTSIZE;
406  register JSAMPROW inptr, above_ptr, below_ptr, outptr;
407  INT32 membersum, neighsum, memberscale, neighscale;
408  int colsum, lastcolsum, nextcolsum;
409
410  /* Expand input data enough to let all the output samples be generated
411   * by the standard loop.  Special-casing padded output would be more
412   * efficient.
413   */
414  expand_right_edge(input_data - 1, cinfo->max_v_samp_factor + 2,
415                    cinfo->image_width, output_cols);
416
417  /* Each of the eight neighbor pixels contributes a fraction SF to the
418   * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
419   * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
420   * Also recall that SF = smoothing_factor / 1024.
421   */
422
423  memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
424  neighscale = cinfo->smoothing_factor * 64; /* scaled SF */
425
426  for (outrow = 0; outrow < compptr->v_samp_factor; outrow++) {
427    outptr = output_data[outrow];
428    inptr = input_data[outrow];
429    above_ptr = input_data[outrow-1];
430    below_ptr = input_data[outrow+1];
431
432    /* Special case for first column */
433    colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
434             GETJSAMPLE(*inptr);
435    membersum = GETJSAMPLE(*inptr++);
436    nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
437                 GETJSAMPLE(*inptr);
438    neighsum = colsum + (colsum - membersum) + nextcolsum;
439    membersum = membersum * memberscale + neighsum * neighscale;
440    *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
441    lastcolsum = colsum; colsum = nextcolsum;
442
443    for (colctr = output_cols - 2; colctr > 0; colctr--) {
444      membersum = GETJSAMPLE(*inptr++);
445      above_ptr++; below_ptr++;
446      nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
447                   GETJSAMPLE(*inptr);
448      neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
449      membersum = membersum * memberscale + neighsum * neighscale;
450      *outptr++ = (JSAMPLE) ((membersum + 32768) >> 16);
451      lastcolsum = colsum; colsum = nextcolsum;
452    }
453
454    /* Special case for last column */
455    membersum = GETJSAMPLE(*inptr);
456    neighsum = lastcolsum + (colsum - membersum) + colsum;
457    membersum = membersum * memberscale + neighsum * neighscale;
458    *outptr = (JSAMPLE) ((membersum + 32768) >> 16);
459
460  }
461}
462
463#endif /* INPUT_SMOOTHING_SUPPORTED */
464
465
466/*
467 * Module initialization routine for downsampling.
468 * Note that we must select a routine for each component.
469 */
470
471GLOBAL(void)
472jinit_downsampler (j_compress_ptr cinfo)
473{
474  my_downsample_ptr downsample;
475  int ci;
476  jpeg_component_info * compptr;
477  boolean smoothok = TRUE;
478
479  downsample = (my_downsample_ptr)
480    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
481                                SIZEOF(my_downsampler));
482  cinfo->downsample = (struct jpeg_downsampler *) downsample;
483  downsample->pub.start_pass = start_pass_downsample;
484  downsample->pub.downsample = sep_downsample;
485  downsample->pub.need_context_rows = FALSE;
486
487  if (cinfo->CCIR601_sampling)
488    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
489
490  /* Verify we can handle the sampling factors, and set up method pointers */
491  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
492       ci++, compptr++) {
493    if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
494        compptr->v_samp_factor == cinfo->max_v_samp_factor) {
495#ifdef INPUT_SMOOTHING_SUPPORTED
496      if (cinfo->smoothing_factor) {
497        downsample->methods[ci] = fullsize_smooth_downsample;
498        downsample->pub.need_context_rows = TRUE;
499      } else
500#endif
501        downsample->methods[ci] = fullsize_downsample;
502    } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
503               compptr->v_samp_factor == cinfo->max_v_samp_factor) {
504      smoothok = FALSE;
505      downsample->methods[ci] = h2v1_downsample;
506    } else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
507               compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
508#ifdef INPUT_SMOOTHING_SUPPORTED
509      if (cinfo->smoothing_factor) {
510        downsample->methods[ci] = h2v2_smooth_downsample;
511        downsample->pub.need_context_rows = TRUE;
512      } else
513#endif
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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