PageRenderTime 71ms CodeModel.GetById 23ms app.highlight 42ms RepoModel.GetById 1ms app.codeStats 0ms

/src/FreeImage/Source/LibJPEG/jdcoefct.c

https://bitbucket.org/cabalistic/ogredeps/
C | 741 lines | 513 code | 66 blank | 162 comment | 139 complexity | f2d9349bf91156527e693f67e2950689 MD5 | raw file
  1/*
  2 * jdcoefct.c
  3 *
  4 * Copyright (C) 1994-1997, Thomas G. Lane.
  5 * Modified 2002-2011 by Guido Vollbeding.
  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 the coefficient buffer controller for decompression.
 10 * This controller is the top level of the JPEG decompressor proper.
 11 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
 12 *
 13 * In buffered-image mode, this controller is the interface between
 14 * input-oriented processing and output-oriented processing.
 15 * Also, the input side (only) is used when reading a file for transcoding.
 16 */
 17
 18#define JPEG_INTERNALS
 19#include "jinclude.h"
 20#include "jpeglib.h"
 21
 22/* Block smoothing is only applicable for progressive JPEG, so: */
 23#ifndef D_PROGRESSIVE_SUPPORTED
 24#undef BLOCK_SMOOTHING_SUPPORTED
 25#endif
 26
 27/* Private buffer controller object */
 28
 29typedef struct {
 30  struct jpeg_d_coef_controller pub; /* public fields */
 31
 32  /* These variables keep track of the current location of the input side. */
 33  /* cinfo->input_iMCU_row is also used for this. */
 34  JDIMENSION MCU_ctr;		/* counts MCUs processed in current row */
 35  int MCU_vert_offset;		/* counts MCU rows within iMCU row */
 36  int MCU_rows_per_iMCU_row;	/* number of such rows needed */
 37
 38  /* The output side's location is represented by cinfo->output_iMCU_row. */
 39
 40  /* In single-pass modes, it's sufficient to buffer just one MCU.
 41   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
 42   * and let the entropy decoder write into that workspace each time.
 43   * (On 80x86, the workspace is FAR even though it's not really very big;
 44   * this is to keep the module interfaces unchanged when a large coefficient
 45   * buffer is necessary.)
 46   * In multi-pass modes, this array points to the current MCU's blocks
 47   * within the virtual arrays; it is used only by the input side.
 48   */
 49  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
 50
 51#ifdef D_MULTISCAN_FILES_SUPPORTED
 52  /* In multi-pass modes, we need a virtual block array for each component. */
 53  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
 54#endif
 55
 56#ifdef BLOCK_SMOOTHING_SUPPORTED
 57  /* When doing block smoothing, we latch coefficient Al values here */
 58  int * coef_bits_latch;
 59#define SAVED_COEFS  6		/* we save coef_bits[0..5] */
 60#endif
 61} my_coef_controller;
 62
 63typedef my_coef_controller * my_coef_ptr;
 64
 65/* Forward declarations */
 66METHODDEF(int) decompress_onepass
 67	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 68#ifdef D_MULTISCAN_FILES_SUPPORTED
 69METHODDEF(int) decompress_data
 70	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 71#endif
 72#ifdef BLOCK_SMOOTHING_SUPPORTED
 73LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
 74METHODDEF(int) decompress_smooth_data
 75	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 76#endif
 77
 78
 79LOCAL(void)
 80start_iMCU_row (j_decompress_ptr cinfo)
 81/* Reset within-iMCU-row counters for a new row (input side) */
 82{
 83  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 84
 85  /* In an interleaved scan, an MCU row is the same as an iMCU row.
 86   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
 87   * But at the bottom of the image, process only what's left.
 88   */
 89  if (cinfo->comps_in_scan > 1) {
 90    coef->MCU_rows_per_iMCU_row = 1;
 91  } else {
 92    if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
 93      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
 94    else
 95      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
 96  }
 97
 98  coef->MCU_ctr = 0;
 99  coef->MCU_vert_offset = 0;
100}
101
102
103/*
104 * Initialize for an input processing pass.
105 */
106
107METHODDEF(void)
108start_input_pass (j_decompress_ptr cinfo)
109{
110  cinfo->input_iMCU_row = 0;
111  start_iMCU_row(cinfo);
112}
113
114
115/*
116 * Initialize for an output processing pass.
117 */
118
119METHODDEF(void)
120start_output_pass (j_decompress_ptr cinfo)
121{
122#ifdef BLOCK_SMOOTHING_SUPPORTED
123  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
124
125  /* If multipass, check to see whether to use block smoothing on this pass */
126  if (coef->pub.coef_arrays != NULL) {
127    if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
128      coef->pub.decompress_data = decompress_smooth_data;
129    else
130      coef->pub.decompress_data = decompress_data;
131  }
132#endif
133  cinfo->output_iMCU_row = 0;
134}
135
136
137/*
138 * Decompress and return some data in the single-pass case.
139 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
140 * Input and output must run in lockstep since we have only a one-MCU buffer.
141 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
142 *
143 * NB: output_buf contains a plane for each component in image,
144 * which we index according to the component's SOF position.
145 */
146
147METHODDEF(int)
148decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
149{
150  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
151  JDIMENSION MCU_col_num;	/* index of current MCU within row */
152  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
153  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
154  int blkn, ci, xindex, yindex, yoffset, useful_width;
155  JSAMPARRAY output_ptr;
156  JDIMENSION start_col, output_col;
157  jpeg_component_info *compptr;
158  inverse_DCT_method_ptr inverse_DCT;
159
160  /* Loop to process as much as one whole iMCU row */
161  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
162       yoffset++) {
163    for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
164	 MCU_col_num++) {
165      /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
166      if (cinfo->lim_Se)	/* can bypass in DC only case */
167	FMEMZERO((void FAR *) coef->MCU_buffer[0],
168		 (size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
169      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
170	/* Suspension forced; update state counters and exit */
171	coef->MCU_vert_offset = yoffset;
172	coef->MCU_ctr = MCU_col_num;
173	return JPEG_SUSPENDED;
174      }
175      /* Determine where data should go in output_buf and do the IDCT thing.
176       * We skip dummy blocks at the right and bottom edges (but blkn gets
177       * incremented past them!).  Note the inner loop relies on having
178       * allocated the MCU_buffer[] blocks sequentially.
179       */
180      blkn = 0;			/* index of current DCT block within MCU */
181      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
182	compptr = cinfo->cur_comp_info[ci];
183	/* Don't bother to IDCT an uninteresting component. */
184	if (! compptr->component_needed) {
185	  blkn += compptr->MCU_blocks;
186	  continue;
187	}
188	inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
189	useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
190						    : compptr->last_col_width;
191	output_ptr = output_buf[compptr->component_index] +
192	  yoffset * compptr->DCT_v_scaled_size;
193	start_col = MCU_col_num * compptr->MCU_sample_width;
194	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
195	  if (cinfo->input_iMCU_row < last_iMCU_row ||
196	      yoffset+yindex < compptr->last_row_height) {
197	    output_col = start_col;
198	    for (xindex = 0; xindex < useful_width; xindex++) {
199	      (*inverse_DCT) (cinfo, compptr,
200			      (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
201			      output_ptr, output_col);
202	      output_col += compptr->DCT_h_scaled_size;
203	    }
204	  }
205	  blkn += compptr->MCU_width;
206	  output_ptr += compptr->DCT_v_scaled_size;
207	}
208      }
209    }
210    /* Completed an MCU row, but perhaps not an iMCU row */
211    coef->MCU_ctr = 0;
212  }
213  /* Completed the iMCU row, advance counters for next one */
214  cinfo->output_iMCU_row++;
215  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
216    start_iMCU_row(cinfo);
217    return JPEG_ROW_COMPLETED;
218  }
219  /* Completed the scan */
220  (*cinfo->inputctl->finish_input_pass) (cinfo);
221  return JPEG_SCAN_COMPLETED;
222}
223
224
225/*
226 * Dummy consume-input routine for single-pass operation.
227 */
228
229METHODDEF(int)
230dummy_consume_data (j_decompress_ptr cinfo)
231{
232  return JPEG_SUSPENDED;	/* Always indicate nothing was done */
233}
234
235
236#ifdef D_MULTISCAN_FILES_SUPPORTED
237
238/*
239 * Consume input data and store it in the full-image coefficient buffer.
240 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
241 * ie, v_samp_factor block rows for each component in the scan.
242 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
243 */
244
245METHODDEF(int)
246consume_data (j_decompress_ptr cinfo)
247{
248  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
249  JDIMENSION MCU_col_num;	/* index of current MCU within row */
250  int blkn, ci, xindex, yindex, yoffset;
251  JDIMENSION start_col;
252  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
253  JBLOCKROW buffer_ptr;
254  jpeg_component_info *compptr;
255
256  /* Align the virtual buffers for the components used in this scan. */
257  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
258    compptr = cinfo->cur_comp_info[ci];
259    buffer[ci] = (*cinfo->mem->access_virt_barray)
260      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
261       cinfo->input_iMCU_row * compptr->v_samp_factor,
262       (JDIMENSION) compptr->v_samp_factor, TRUE);
263    /* Note: entropy decoder expects buffer to be zeroed,
264     * but this is handled automatically by the memory manager
265     * because we requested a pre-zeroed array.
266     */
267  }
268
269  /* Loop to process one whole iMCU row */
270  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
271       yoffset++) {
272    for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
273	 MCU_col_num++) {
274      /* Construct list of pointers to DCT blocks belonging to this MCU */
275      blkn = 0;			/* index of current DCT block within MCU */
276      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
277	compptr = cinfo->cur_comp_info[ci];
278	start_col = MCU_col_num * compptr->MCU_width;
279	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
280	  buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
281	  for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
282	    coef->MCU_buffer[blkn++] = buffer_ptr++;
283	  }
284	}
285      }
286      /* Try to fetch the MCU. */
287      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
288	/* Suspension forced; update state counters and exit */
289	coef->MCU_vert_offset = yoffset;
290	coef->MCU_ctr = MCU_col_num;
291	return JPEG_SUSPENDED;
292      }
293    }
294    /* Completed an MCU row, but perhaps not an iMCU row */
295    coef->MCU_ctr = 0;
296  }
297  /* Completed the iMCU row, advance counters for next one */
298  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
299    start_iMCU_row(cinfo);
300    return JPEG_ROW_COMPLETED;
301  }
302  /* Completed the scan */
303  (*cinfo->inputctl->finish_input_pass) (cinfo);
304  return JPEG_SCAN_COMPLETED;
305}
306
307
308/*
309 * Decompress and return some data in the multi-pass case.
310 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
311 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
312 *
313 * NB: output_buf contains a plane for each component in image.
314 */
315
316METHODDEF(int)
317decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
318{
319  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
320  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
321  JDIMENSION block_num;
322  int ci, block_row, block_rows;
323  JBLOCKARRAY buffer;
324  JBLOCKROW buffer_ptr;
325  JSAMPARRAY output_ptr;
326  JDIMENSION output_col;
327  jpeg_component_info *compptr;
328  inverse_DCT_method_ptr inverse_DCT;
329
330  /* Force some input to be done if we are getting ahead of the input. */
331  while (cinfo->input_scan_number < cinfo->output_scan_number ||
332	 (cinfo->input_scan_number == cinfo->output_scan_number &&
333	  cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
334    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
335      return JPEG_SUSPENDED;
336  }
337
338  /* OK, output from the virtual arrays. */
339  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
340       ci++, compptr++) {
341    /* Don't bother to IDCT an uninteresting component. */
342    if (! compptr->component_needed)
343      continue;
344    /* Align the virtual buffer for this component. */
345    buffer = (*cinfo->mem->access_virt_barray)
346      ((j_common_ptr) cinfo, coef->whole_image[ci],
347       cinfo->output_iMCU_row * compptr->v_samp_factor,
348       (JDIMENSION) compptr->v_samp_factor, FALSE);
349    /* Count non-dummy DCT block rows in this iMCU row. */
350    if (cinfo->output_iMCU_row < last_iMCU_row)
351      block_rows = compptr->v_samp_factor;
352    else {
353      /* NB: can't use last_row_height here; it is input-side-dependent! */
354      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
355      if (block_rows == 0) block_rows = compptr->v_samp_factor;
356    }
357    inverse_DCT = cinfo->idct->inverse_DCT[ci];
358    output_ptr = output_buf[ci];
359    /* Loop over all DCT blocks to be processed. */
360    for (block_row = 0; block_row < block_rows; block_row++) {
361      buffer_ptr = buffer[block_row];
362      output_col = 0;
363      for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
364	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
365			output_ptr, output_col);
366	buffer_ptr++;
367	output_col += compptr->DCT_h_scaled_size;
368      }
369      output_ptr += compptr->DCT_v_scaled_size;
370    }
371  }
372
373  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
374    return JPEG_ROW_COMPLETED;
375  return JPEG_SCAN_COMPLETED;
376}
377
378#endif /* D_MULTISCAN_FILES_SUPPORTED */
379
380
381#ifdef BLOCK_SMOOTHING_SUPPORTED
382
383/*
384 * This code applies interblock smoothing as described by section K.8
385 * of the JPEG standard: the first 5 AC coefficients are estimated from
386 * the DC values of a DCT block and its 8 neighboring blocks.
387 * We apply smoothing only for progressive JPEG decoding, and only if
388 * the coefficients it can estimate are not yet known to full precision.
389 */
390
391/* Natural-order array positions of the first 5 zigzag-order coefficients */
392#define Q01_POS  1
393#define Q10_POS  8
394#define Q20_POS  16
395#define Q11_POS  9
396#define Q02_POS  2
397
398/*
399 * Determine whether block smoothing is applicable and safe.
400 * We also latch the current states of the coef_bits[] entries for the
401 * AC coefficients; otherwise, if the input side of the decompressor
402 * advances into a new scan, we might think the coefficients are known
403 * more accurately than they really are.
404 */
405
406LOCAL(boolean)
407smoothing_ok (j_decompress_ptr cinfo)
408{
409  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
410  boolean smoothing_useful = FALSE;
411  int ci, coefi;
412  jpeg_component_info *compptr;
413  JQUANT_TBL * qtable;
414  int * coef_bits;
415  int * coef_bits_latch;
416
417  if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
418    return FALSE;
419
420  /* Allocate latch area if not already done */
421  if (coef->coef_bits_latch == NULL)
422    coef->coef_bits_latch = (int *)
423      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
424				  cinfo->num_components *
425				  (SAVED_COEFS * SIZEOF(int)));
426  coef_bits_latch = coef->coef_bits_latch;
427
428  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
429       ci++, compptr++) {
430    /* All components' quantization values must already be latched. */
431    if ((qtable = compptr->quant_table) == NULL)
432      return FALSE;
433    /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
434    if (qtable->quantval[0] == 0 ||
435	qtable->quantval[Q01_POS] == 0 ||
436	qtable->quantval[Q10_POS] == 0 ||
437	qtable->quantval[Q20_POS] == 0 ||
438	qtable->quantval[Q11_POS] == 0 ||
439	qtable->quantval[Q02_POS] == 0)
440      return FALSE;
441    /* DC values must be at least partly known for all components. */
442    coef_bits = cinfo->coef_bits[ci];
443    if (coef_bits[0] < 0)
444      return FALSE;
445    /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
446    for (coefi = 1; coefi <= 5; coefi++) {
447      coef_bits_latch[coefi] = coef_bits[coefi];
448      if (coef_bits[coefi] != 0)
449	smoothing_useful = TRUE;
450    }
451    coef_bits_latch += SAVED_COEFS;
452  }
453
454  return smoothing_useful;
455}
456
457
458/*
459 * Variant of decompress_data for use when doing block smoothing.
460 */
461
462METHODDEF(int)
463decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
464{
465  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
466  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
467  JDIMENSION block_num, last_block_column;
468  int ci, block_row, block_rows, access_rows;
469  JBLOCKARRAY buffer;
470  JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
471  JSAMPARRAY output_ptr;
472  JDIMENSION output_col;
473  jpeg_component_info *compptr;
474  inverse_DCT_method_ptr inverse_DCT;
475  boolean first_row, last_row;
476  JBLOCK workspace;
477  int *coef_bits;
478  JQUANT_TBL *quanttbl;
479  INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
480  int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
481  int Al, pred;
482
483  /* Force some input to be done if we are getting ahead of the input. */
484  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
485	 ! cinfo->inputctl->eoi_reached) {
486    if (cinfo->input_scan_number == cinfo->output_scan_number) {
487      /* If input is working on current scan, we ordinarily want it to
488       * have completed the current row.  But if input scan is DC,
489       * we want it to keep one row ahead so that next block row's DC
490       * values are up to date.
491       */
492      JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
493      if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
494	break;
495    }
496    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
497      return JPEG_SUSPENDED;
498  }
499
500  /* OK, output from the virtual arrays. */
501  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
502       ci++, compptr++) {
503    /* Don't bother to IDCT an uninteresting component. */
504    if (! compptr->component_needed)
505      continue;
506    /* Count non-dummy DCT block rows in this iMCU row. */
507    if (cinfo->output_iMCU_row < last_iMCU_row) {
508      block_rows = compptr->v_samp_factor;
509      access_rows = block_rows * 2; /* this and next iMCU row */
510      last_row = FALSE;
511    } else {
512      /* NB: can't use last_row_height here; it is input-side-dependent! */
513      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
514      if (block_rows == 0) block_rows = compptr->v_samp_factor;
515      access_rows = block_rows; /* this iMCU row only */
516      last_row = TRUE;
517    }
518    /* Align the virtual buffer for this component. */
519    if (cinfo->output_iMCU_row > 0) {
520      access_rows += compptr->v_samp_factor; /* prior iMCU row too */
521      buffer = (*cinfo->mem->access_virt_barray)
522	((j_common_ptr) cinfo, coef->whole_image[ci],
523	 (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
524	 (JDIMENSION) access_rows, FALSE);
525      buffer += compptr->v_samp_factor;	/* point to current iMCU row */
526      first_row = FALSE;
527    } else {
528      buffer = (*cinfo->mem->access_virt_barray)
529	((j_common_ptr) cinfo, coef->whole_image[ci],
530	 (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
531      first_row = TRUE;
532    }
533    /* Fetch component-dependent info */
534    coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
535    quanttbl = compptr->quant_table;
536    Q00 = quanttbl->quantval[0];
537    Q01 = quanttbl->quantval[Q01_POS];
538    Q10 = quanttbl->quantval[Q10_POS];
539    Q20 = quanttbl->quantval[Q20_POS];
540    Q11 = quanttbl->quantval[Q11_POS];
541    Q02 = quanttbl->quantval[Q02_POS];
542    inverse_DCT = cinfo->idct->inverse_DCT[ci];
543    output_ptr = output_buf[ci];
544    /* Loop over all DCT blocks to be processed. */
545    for (block_row = 0; block_row < block_rows; block_row++) {
546      buffer_ptr = buffer[block_row];
547      if (first_row && block_row == 0)
548	prev_block_row = buffer_ptr;
549      else
550	prev_block_row = buffer[block_row-1];
551      if (last_row && block_row == block_rows-1)
552	next_block_row = buffer_ptr;
553      else
554	next_block_row = buffer[block_row+1];
555      /* We fetch the surrounding DC values using a sliding-register approach.
556       * Initialize all nine here so as to do the right thing on narrow pics.
557       */
558      DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
559      DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
560      DC7 = DC8 = DC9 = (int) next_block_row[0][0];
561      output_col = 0;
562      last_block_column = compptr->width_in_blocks - 1;
563      for (block_num = 0; block_num <= last_block_column; block_num++) {
564	/* Fetch current DCT block into workspace so we can modify it. */
565	jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
566	/* Update DC values */
567	if (block_num < last_block_column) {
568	  DC3 = (int) prev_block_row[1][0];
569	  DC6 = (int) buffer_ptr[1][0];
570	  DC9 = (int) next_block_row[1][0];
571	}
572	/* Compute coefficient estimates per K.8.
573	 * An estimate is applied only if coefficient is still zero,
574	 * and is not known to be fully accurate.
575	 */
576	/* AC01 */
577	if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
578	  num = 36 * Q00 * (DC4 - DC6);
579	  if (num >= 0) {
580	    pred = (int) (((Q01<<7) + num) / (Q01<<8));
581	    if (Al > 0 && pred >= (1<<Al))
582	      pred = (1<<Al)-1;
583	  } else {
584	    pred = (int) (((Q01<<7) - num) / (Q01<<8));
585	    if (Al > 0 && pred >= (1<<Al))
586	      pred = (1<<Al)-1;
587	    pred = -pred;
588	  }
589	  workspace[1] = (JCOEF) pred;
590	}
591	/* AC10 */
592	if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
593	  num = 36 * Q00 * (DC2 - DC8);
594	  if (num >= 0) {
595	    pred = (int) (((Q10<<7) + num) / (Q10<<8));
596	    if (Al > 0 && pred >= (1<<Al))
597	      pred = (1<<Al)-1;
598	  } else {
599	    pred = (int) (((Q10<<7) - num) / (Q10<<8));
600	    if (Al > 0 && pred >= (1<<Al))
601	      pred = (1<<Al)-1;
602	    pred = -pred;
603	  }
604	  workspace[8] = (JCOEF) pred;
605	}
606	/* AC20 */
607	if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
608	  num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
609	  if (num >= 0) {
610	    pred = (int) (((Q20<<7) + num) / (Q20<<8));
611	    if (Al > 0 && pred >= (1<<Al))
612	      pred = (1<<Al)-1;
613	  } else {
614	    pred = (int) (((Q20<<7) - num) / (Q20<<8));
615	    if (Al > 0 && pred >= (1<<Al))
616	      pred = (1<<Al)-1;
617	    pred = -pred;
618	  }
619	  workspace[16] = (JCOEF) pred;
620	}
621	/* AC11 */
622	if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
623	  num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
624	  if (num >= 0) {
625	    pred = (int) (((Q11<<7) + num) / (Q11<<8));
626	    if (Al > 0 && pred >= (1<<Al))
627	      pred = (1<<Al)-1;
628	  } else {
629	    pred = (int) (((Q11<<7) - num) / (Q11<<8));
630	    if (Al > 0 && pred >= (1<<Al))
631	      pred = (1<<Al)-1;
632	    pred = -pred;
633	  }
634	  workspace[9] = (JCOEF) pred;
635	}
636	/* AC02 */
637	if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
638	  num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
639	  if (num >= 0) {
640	    pred = (int) (((Q02<<7) + num) / (Q02<<8));
641	    if (Al > 0 && pred >= (1<<Al))
642	      pred = (1<<Al)-1;
643	  } else {
644	    pred = (int) (((Q02<<7) - num) / (Q02<<8));
645	    if (Al > 0 && pred >= (1<<Al))
646	      pred = (1<<Al)-1;
647	    pred = -pred;
648	  }
649	  workspace[2] = (JCOEF) pred;
650	}
651	/* OK, do the IDCT */
652	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
653			output_ptr, output_col);
654	/* Advance for next column */
655	DC1 = DC2; DC2 = DC3;
656	DC4 = DC5; DC5 = DC6;
657	DC7 = DC8; DC8 = DC9;
658	buffer_ptr++, prev_block_row++, next_block_row++;
659	output_col += compptr->DCT_h_scaled_size;
660      }
661      output_ptr += compptr->DCT_v_scaled_size;
662    }
663  }
664
665  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
666    return JPEG_ROW_COMPLETED;
667  return JPEG_SCAN_COMPLETED;
668}
669
670#endif /* BLOCK_SMOOTHING_SUPPORTED */
671
672
673/*
674 * Initialize coefficient buffer controller.
675 */
676
677GLOBAL(void)
678jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
679{
680  my_coef_ptr coef;
681
682  coef = (my_coef_ptr)
683    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
684				SIZEOF(my_coef_controller));
685  cinfo->coef = (struct jpeg_d_coef_controller *) coef;
686  coef->pub.start_input_pass = start_input_pass;
687  coef->pub.start_output_pass = start_output_pass;
688#ifdef BLOCK_SMOOTHING_SUPPORTED
689  coef->coef_bits_latch = NULL;
690#endif
691
692  /* Create the coefficient buffer. */
693  if (need_full_buffer) {
694#ifdef D_MULTISCAN_FILES_SUPPORTED
695    /* Allocate a full-image virtual array for each component, */
696    /* padded to a multiple of samp_factor DCT blocks in each direction. */
697    /* Note we ask for a pre-zeroed array. */
698    int ci, access_rows;
699    jpeg_component_info *compptr;
700
701    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
702	 ci++, compptr++) {
703      access_rows = compptr->v_samp_factor;
704#ifdef BLOCK_SMOOTHING_SUPPORTED
705      /* If block smoothing could be used, need a bigger window */
706      if (cinfo->progressive_mode)
707	access_rows *= 3;
708#endif
709      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
710	((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
711	 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
712				(long) compptr->h_samp_factor),
713	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
714				(long) compptr->v_samp_factor),
715	 (JDIMENSION) access_rows);
716    }
717    coef->pub.consume_data = consume_data;
718    coef->pub.decompress_data = decompress_data;
719    coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
720#else
721    ERREXIT(cinfo, JERR_NOT_COMPILED);
722#endif
723  } else {
724    /* We only need a single-MCU buffer. */
725    JBLOCKROW buffer;
726    int i;
727
728    buffer = (JBLOCKROW)
729      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
730				  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
731    for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
732      coef->MCU_buffer[i] = buffer + i;
733    }
734    if (cinfo->lim_Se == 0)	/* DC only case: want to bypass later */
735      FMEMZERO((void FAR *) buffer,
736	       (size_t) (D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK)));
737    coef->pub.consume_data = dummy_consume_data;
738    coef->pub.decompress_data = decompress_onepass;
739    coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
740  }
741}