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