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/media/libjpeg/jccoefct.c

http://github.com/zpao/v8monkey
C | 449 lines | 279 code | 44 blank | 126 comment | 45 complexity | 5c4997ec8ba5559dd1b4c87faab144d7 MD5 | raw file
  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
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 FAR *) 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 FAR *) 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 FAR *) 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 FAR *) 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}