source: trunk/libjpeg/jccoefct.c @ 283

Last change on this file since 283 was 283, checked in by rbri, 12 years ago

JPEG plugin: libjpeg updated to version 7

File size: 16.7 KB
Line 
1/*
2 * jccoefct.c
3 *
4 * Copyright (C) 1994-1997, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains the coefficient buffer controller for compression.
9 * This controller is the top level of the JPEG compressor proper.
10 * The coefficient buffer lies between forward-DCT and entropy encoding steps.
11 */
12
13#define JPEG_INTERNALS
14#include "jinclude.h"
15#include "jpeglib.h"
16
17
18/* We use a full-image coefficient buffer when doing Huffman optimization,
19 * and also for writing multiple-scan JPEG files.  In all cases, the DCT
20 * step is run during the first pass, and subsequent passes need only read
21 * the buffered coefficients.
22 */
23#ifdef ENTROPY_OPT_SUPPORTED
24#define FULL_COEF_BUFFER_SUPPORTED
25#else
26#ifdef C_MULTISCAN_FILES_SUPPORTED
27#define FULL_COEF_BUFFER_SUPPORTED
28#endif
29#endif
30
31
32/* Private buffer controller object */
33
34typedef struct {
35  struct jpeg_c_coef_controller pub; /* public fields */
36
37  JDIMENSION iMCU_row_num;      /* iMCU row # within image */
38  JDIMENSION mcu_ctr;           /* counts MCUs processed in current row */
39  int MCU_vert_offset;          /* counts MCU rows within iMCU row */
40  int MCU_rows_per_iMCU_row;    /* number of such rows needed */
41
42  /* For single-pass compression, it's sufficient to buffer just one MCU
43   * (although this may prove a bit slow in practice).  We allocate a
44   * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
45   * MCU constructed and sent.  (On 80x86, the workspace is FAR even though
46   * it's not really very big; this is to keep the module interfaces unchanged
47   * when a large coefficient buffer is necessary.)
48   * In multi-pass modes, this array points to the current MCU's blocks
49   * within the virtual arrays.
50   */
51  JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
52
53  /* In multi-pass modes, we need a virtual block array for each component. */
54  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
55} my_coef_controller;
56
57typedef my_coef_controller * my_coef_ptr;
58
59
60/* Forward declarations */
61METHODDEF(boolean) compress_data
62    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
63#ifdef FULL_COEF_BUFFER_SUPPORTED
64METHODDEF(boolean) compress_first_pass
65    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
66METHODDEF(boolean) compress_output
67    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
68#endif
69
70
71LOCAL(void)
72start_iMCU_row (j_compress_ptr cinfo)
73/* Reset within-iMCU-row counters for a new row */
74{
75  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
76
77  /* In an interleaved scan, an MCU row is the same as an iMCU row.
78   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
79   * But at the bottom of the image, process only what's left.
80   */
81  if (cinfo->comps_in_scan > 1) {
82    coef->MCU_rows_per_iMCU_row = 1;
83  } else {
84    if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
85      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
86    else
87      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
88  }
89
90  coef->mcu_ctr = 0;
91  coef->MCU_vert_offset = 0;
92}
93
94
95/*
96 * Initialize for a processing pass.
97 */
98
99METHODDEF(void)
100start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
101{
102  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
103
104  coef->iMCU_row_num = 0;
105  start_iMCU_row(cinfo);
106
107  switch (pass_mode) {
108  case JBUF_PASS_THRU:
109    if (coef->whole_image[0] != NULL)
110      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
111    coef->pub.compress_data = compress_data;
112    break;
113#ifdef FULL_COEF_BUFFER_SUPPORTED
114  case JBUF_SAVE_AND_PASS:
115    if (coef->whole_image[0] == NULL)
116      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
117    coef->pub.compress_data = compress_first_pass;
118    break;
119  case JBUF_CRANK_DEST:
120    if (coef->whole_image[0] == NULL)
121      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
122    coef->pub.compress_data = compress_output;
123    break;
124#endif
125  default:
126    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
127    break;
128  }
129}
130
131
132/*
133 * Process some data in the single-pass case.
134 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
135 * per call, ie, v_samp_factor block rows for each component in the image.
136 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
137 *
138 * NB: input_buf contains a plane for each component in image,
139 * which we index according to the component's SOF position.
140 */
141
142METHODDEF(boolean)
143compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
144{
145  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
146  JDIMENSION MCU_col_num;       /* index of current MCU within row */
147  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
148  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
149  int blkn, bi, ci, yindex, yoffset, blockcnt;
150  JDIMENSION ypos, xpos;
151  jpeg_component_info *compptr;
152  forward_DCT_ptr forward_DCT;
153
154  /* Loop to write as much as one whole iMCU row */
155  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
156       yoffset++) {
157    for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
158         MCU_col_num++) {
159      /* Determine where data comes from in input_buf and do the DCT thing.
160       * Each call on forward_DCT processes a horizontal row of DCT blocks
161       * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
162       * sequentially.  Dummy blocks at the right or bottom edge are filled in
163       * specially.  The data in them does not matter for image reconstruction,
164       * so we fill them with values that will encode to the smallest amount of
165       * data, viz: all zeroes in the AC entries, DC entries equal to previous
166       * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
167       */
168      blkn = 0;
169      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
170        compptr = cinfo->cur_comp_info[ci];
171        forward_DCT = cinfo->fdct->forward_DCT[compptr->component_index];
172        blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
173                                                : compptr->last_col_width;
174        xpos = MCU_col_num * compptr->MCU_sample_width;
175        ypos = yoffset * compptr->DCT_v_scaled_size;
176        /* ypos == (yoffset+yindex) * DCTSIZE */
177        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
178          if (coef->iMCU_row_num < last_iMCU_row ||
179              yoffset+yindex < compptr->last_row_height) {
180            (*forward_DCT) (cinfo, compptr,
181                            input_buf[compptr->component_index],
182                            coef->MCU_buffer[blkn],
183                            ypos, xpos, (JDIMENSION) blockcnt);
184            if (blockcnt < compptr->MCU_width) {
185              /* Create some dummy blocks at the right edge of the image. */
186              jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
187                        (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
188              for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
189                coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
190              }
191            }
192          } else {
193            /* Create a row of dummy blocks at the bottom of the image. */
194            jzero_far((void FAR *) coef->MCU_buffer[blkn],
195                      compptr->MCU_width * SIZEOF(JBLOCK));
196            for (bi = 0; bi < compptr->MCU_width; bi++) {
197              coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
198            }
199          }
200          blkn += compptr->MCU_width;
201          ypos += compptr->DCT_v_scaled_size;
202        }
203      }
204      /* Try to write the MCU.  In event of a suspension failure, we will
205       * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
206       */
207      if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
208        /* Suspension forced; update state counters and exit */
209        coef->MCU_vert_offset = yoffset;
210        coef->mcu_ctr = MCU_col_num;
211        return FALSE;
212      }
213    }
214    /* Completed an MCU row, but perhaps not an iMCU row */
215    coef->mcu_ctr = 0;
216  }
217  /* Completed the iMCU row, advance counters for next one */
218  coef->iMCU_row_num++;
219  start_iMCU_row(cinfo);
220  return TRUE;
221}
222
223
224#ifdef FULL_COEF_BUFFER_SUPPORTED
225
226/*
227 * Process some data in the first pass of a multi-pass case.
228 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
229 * per call, ie, v_samp_factor block rows for each component in the image.
230 * This amount of data is read from the source buffer, DCT'd and quantized,
231 * and saved into the virtual arrays.  We also generate suitable dummy blocks
232 * as needed at the right and lower edges.  (The dummy blocks are constructed
233 * in the virtual arrays, which have been padded appropriately.)  This makes
234 * it possible for subsequent passes not to worry about real vs. dummy blocks.
235 *
236 * We must also emit the data to the entropy encoder.  This is conveniently
237 * done by calling compress_output() after we've loaded the current strip
238 * of the virtual arrays.
239 *
240 * NB: input_buf contains a plane for each component in image.  All
241 * components are DCT'd and loaded into the virtual arrays in this pass.
242 * However, it may be that only a subset of the components are emitted to
243 * the entropy encoder during this first pass; be careful about looking
244 * at the scan-dependent variables (MCU dimensions, etc).
245 */
246
247METHODDEF(boolean)
248compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
249{
250  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
251  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
252  JDIMENSION blocks_across, MCUs_across, MCUindex;
253  int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
254  JCOEF lastDC;
255  jpeg_component_info *compptr;
256  JBLOCKARRAY buffer;
257  JBLOCKROW thisblockrow, lastblockrow;
258  forward_DCT_ptr forward_DCT;
259
260  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
261       ci++, compptr++) {
262    /* Align the virtual buffer for this component. */
263    buffer = (*cinfo->mem->access_virt_barray)
264      ((j_common_ptr) cinfo, coef->whole_image[ci],
265       coef->iMCU_row_num * compptr->v_samp_factor,
266       (JDIMENSION) compptr->v_samp_factor, TRUE);
267    /* Count non-dummy DCT block rows in this iMCU row. */
268    if (coef->iMCU_row_num < last_iMCU_row)
269      block_rows = compptr->v_samp_factor;
270    else {
271      /* NB: can't use last_row_height here, since may not be set! */
272      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
273      if (block_rows == 0) block_rows = compptr->v_samp_factor;
274    }
275    blocks_across = compptr->width_in_blocks;
276    h_samp_factor = compptr->h_samp_factor;
277    /* Count number of dummy blocks to be added at the right margin. */
278    ndummy = (int) (blocks_across % h_samp_factor);
279    if (ndummy > 0)
280      ndummy = h_samp_factor - ndummy;
281    forward_DCT = cinfo->fdct->forward_DCT[ci];
282    /* Perform DCT for all non-dummy blocks in this iMCU row.  Each call
283     * on forward_DCT processes a complete horizontal row of DCT blocks.
284     */
285    for (block_row = 0; block_row < block_rows; block_row++) {
286      thisblockrow = buffer[block_row];
287      (*forward_DCT) (cinfo, compptr, input_buf[ci], thisblockrow,
288                      (JDIMENSION) (block_row * compptr->DCT_v_scaled_size),
289                      (JDIMENSION) 0, blocks_across);
290      if (ndummy > 0) {
291        /* Create dummy blocks at the right edge of the image. */
292        thisblockrow += blocks_across; /* => first dummy block */
293        jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
294        lastDC = thisblockrow[-1][0];
295        for (bi = 0; bi < ndummy; bi++) {
296          thisblockrow[bi][0] = lastDC;
297        }
298      }
299    }
300    /* If at end of image, create dummy block rows as needed.
301     * The tricky part here is that within each MCU, we want the DC values
302     * of the dummy blocks to match the last real block's DC value.
303     * This squeezes a few more bytes out of the resulting file...
304     */
305    if (coef->iMCU_row_num == last_iMCU_row) {
306      blocks_across += ndummy;  /* include lower right corner */
307      MCUs_across = blocks_across / h_samp_factor;
308      for (block_row = block_rows; block_row < compptr->v_samp_factor;
309           block_row++) {
310        thisblockrow = buffer[block_row];
311        lastblockrow = buffer[block_row-1];
312        jzero_far((void FAR *) thisblockrow,
313                  (size_t) (blocks_across * SIZEOF(JBLOCK)));
314        for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
315          lastDC = lastblockrow[h_samp_factor-1][0];
316          for (bi = 0; bi < h_samp_factor; bi++) {
317            thisblockrow[bi][0] = lastDC;
318          }
319          thisblockrow += h_samp_factor; /* advance to next MCU in row */
320          lastblockrow += h_samp_factor;
321        }
322      }
323    }
324  }
325  /* NB: compress_output will increment iMCU_row_num if successful.
326   * A suspension return will result in redoing all the work above next time.
327   */
328
329  /* Emit data to the entropy encoder, sharing code with subsequent passes */
330  return compress_output(cinfo, input_buf);
331}
332
333
334/*
335 * Process some data in subsequent passes of a multi-pass case.
336 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
337 * per call, ie, v_samp_factor block rows for each component in the scan.
338 * The data is obtained from the virtual arrays and fed to the entropy coder.
339 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
340 *
341 * NB: input_buf is ignored; it is likely to be a NULL pointer.
342 */
343
344METHODDEF(boolean)
345compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
346{
347  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
348  JDIMENSION MCU_col_num;       /* index of current MCU within row */
349  int blkn, ci, xindex, yindex, yoffset;
350  JDIMENSION start_col;
351  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
352  JBLOCKROW buffer_ptr;
353  jpeg_component_info *compptr;
354
355  /* Align the virtual buffers for the components used in this scan.
356   * NB: during first pass, this is safe only because the buffers will
357   * already be aligned properly, so jmemmgr.c won't need to do any I/O.
358   */
359  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
360    compptr = cinfo->cur_comp_info[ci];
361    buffer[ci] = (*cinfo->mem->access_virt_barray)
362      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
363       coef->iMCU_row_num * compptr->v_samp_factor,
364       (JDIMENSION) compptr->v_samp_factor, FALSE);
365  }
366
367  /* Loop to process one whole iMCU row */
368  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
369       yoffset++) {
370    for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
371         MCU_col_num++) {
372      /* Construct list of pointers to DCT blocks belonging to this MCU */
373      blkn = 0;                 /* index of current DCT block within MCU */
374      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
375        compptr = cinfo->cur_comp_info[ci];
376        start_col = MCU_col_num * compptr->MCU_width;
377        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
378          buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
379          for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
380            coef->MCU_buffer[blkn++] = buffer_ptr++;
381          }
382        }
383      }
384      /* Try to write the MCU. */
385      if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
386        /* Suspension forced; update state counters and exit */
387        coef->MCU_vert_offset = yoffset;
388        coef->mcu_ctr = MCU_col_num;
389        return FALSE;
390      }
391    }
392    /* Completed an MCU row, but perhaps not an iMCU row */
393    coef->mcu_ctr = 0;
394  }
395  /* Completed the iMCU row, advance counters for next one */
396  coef->iMCU_row_num++;
397  start_iMCU_row(cinfo);
398  return TRUE;
399}
400
401#endif /* FULL_COEF_BUFFER_SUPPORTED */
402
403
404/*
405 * Initialize coefficient buffer controller.
406 */
407
408GLOBAL(void)
409jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
410{
411  my_coef_ptr coef;
412
413  coef = (my_coef_ptr)
414    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
415                                SIZEOF(my_coef_controller));
416  cinfo->coef = (struct jpeg_c_coef_controller *) coef;
417  coef->pub.start_pass = start_pass_coef;
418
419  /* Create the coefficient buffer. */
420  if (need_full_buffer) {
421#ifdef FULL_COEF_BUFFER_SUPPORTED
422    /* Allocate a full-image virtual array for each component, */
423    /* padded to a multiple of samp_factor DCT blocks in each direction. */
424    int ci;
425    jpeg_component_info *compptr;
426
427    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
428         ci++, compptr++) {
429      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
430        ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
431         (JDIMENSION) jround_up((long) compptr->width_in_blocks,
432                                (long) compptr->h_samp_factor),
433         (JDIMENSION) jround_up((long) compptr->height_in_blocks,
434                                (long) compptr->v_samp_factor),
435         (JDIMENSION) compptr->v_samp_factor);
436    }
437#else
438    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
439#endif
440  } else {
441    /* We only need a single-MCU buffer. */
442    JBLOCKROW buffer;
443    int i;
444
445    buffer = (JBLOCKROW)
446      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
447                                  C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
448    for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
449      coef->MCU_buffer[i] = buffer + i;
450    }
451    coef->whole_image[0] = NULL; /* flag for no virtual arrays */
452  }
453}
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