source: trunk/libjpeg/jdcoefct.c @ 136

Last change on this file since 136 was 15, checked in by Eugene Romanenko, 16 years ago

needed libs update

File size: 25.3 KB
Line 
1/*
2 * jdcoefct.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 decompression.
9 * This controller is the top level of the JPEG decompressor proper.
10 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
11 *
12 * In buffered-image mode, this controller is the interface between
13 * input-oriented processing and output-oriented processing.
14 * Also, the input side (only) is used when reading a file for transcoding.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20
21/* Block smoothing is only applicable for progressive JPEG, so: */
22#ifndef D_PROGRESSIVE_SUPPORTED
23#undef BLOCK_SMOOTHING_SUPPORTED
24#endif
25
26/* Private buffer controller object */
27
28typedef struct {
29  struct jpeg_d_coef_controller pub; /* public fields */
30
31  /* These variables keep track of the current location of the input side. */
32  /* cinfo->input_iMCU_row is also used for this. */
33  JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */
34  int MCU_vert_offset;          /* counts MCU rows within iMCU row */
35  int MCU_rows_per_iMCU_row;    /* number of such rows needed */
36
37  /* The output side's location is represented by cinfo->output_iMCU_row. */
38
39  /* In single-pass modes, it's sufficient to buffer just one MCU.
40   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
41   * and let the entropy decoder write into that workspace each time.
42   * (On 80x86, the workspace is FAR even though it's not really very big;
43   * this is to keep the module interfaces unchanged when a large coefficient
44   * buffer is necessary.)
45   * In multi-pass modes, this array points to the current MCU's blocks
46   * within the virtual arrays; it is used only by the input side.
47   */
48  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
49
50#ifdef D_MULTISCAN_FILES_SUPPORTED
51  /* In multi-pass modes, we need a virtual block array for each component. */
52  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
53#endif
54
55#ifdef BLOCK_SMOOTHING_SUPPORTED
56  /* When doing block smoothing, we latch coefficient Al values here */
57  int * coef_bits_latch;
58#define SAVED_COEFS  6          /* we save coef_bits[0..5] */
59#endif
60} my_coef_controller;
61
62typedef my_coef_controller * my_coef_ptr;
63
64/* Forward declarations */
65METHODDEF(int) decompress_onepass
66        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
67#ifdef D_MULTISCAN_FILES_SUPPORTED
68METHODDEF(int) decompress_data
69        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
70#endif
71#ifdef BLOCK_SMOOTHING_SUPPORTED
72LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
73METHODDEF(int) decompress_smooth_data
74        JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
75#endif
76
77
78LOCAL(void)
79start_iMCU_row (j_decompress_ptr cinfo)
80/* Reset within-iMCU-row counters for a new row (input side) */
81{
82  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
83
84  /* In an interleaved scan, an MCU row is the same as an iMCU row.
85   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
86   * But at the bottom of the image, process only what's left.
87   */
88  if (cinfo->comps_in_scan > 1) {
89    coef->MCU_rows_per_iMCU_row = 1;
90  } else {
91    if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
92      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
93    else
94      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
95  }
96
97  coef->MCU_ctr = 0;
98  coef->MCU_vert_offset = 0;
99}
100
101
102/*
103 * Initialize for an input processing pass.
104 */
105
106METHODDEF(void)
107start_input_pass (j_decompress_ptr cinfo)
108{
109  cinfo->input_iMCU_row = 0;
110  start_iMCU_row(cinfo);
111}
112
113
114/*
115 * Initialize for an output processing pass.
116 */
117
118METHODDEF(void)
119start_output_pass (j_decompress_ptr cinfo)
120{
121#ifdef BLOCK_SMOOTHING_SUPPORTED
122  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
123
124  /* If multipass, check to see whether to use block smoothing on this pass */
125  if (coef->pub.coef_arrays != NULL) {
126    if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
127      coef->pub.decompress_data = decompress_smooth_data;
128    else
129      coef->pub.decompress_data = decompress_data;
130  }
131#endif
132  cinfo->output_iMCU_row = 0;
133}
134
135
136/*
137 * Decompress and return some data in the single-pass case.
138 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
139 * Input and output must run in lockstep since we have only a one-MCU buffer.
140 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
141 *
142 * NB: output_buf contains a plane for each component in image,
143 * which we index according to the component's SOF position.
144 */
145
146METHODDEF(int)
147decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
148{
149  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
150  JDIMENSION MCU_col_num;       /* index of current MCU within row */
151  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
152  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
153  int blkn, ci, xindex, yindex, yoffset, useful_width;
154  JSAMPARRAY output_ptr;
155  JDIMENSION start_col, output_col;
156  jpeg_component_info *compptr;
157  inverse_DCT_method_ptr inverse_DCT;
158
159  /* Loop to process as much as one whole iMCU row */
160  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
161       yoffset++) {
162    for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
163         MCU_col_num++) {
164      /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
165      jzero_far((void FAR *) coef->MCU_buffer[0],
166                (size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
167      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
168        /* Suspension forced; update state counters and exit */
169        coef->MCU_vert_offset = yoffset;
170        coef->MCU_ctr = MCU_col_num;
171        return JPEG_SUSPENDED;
172      }
173      /* Determine where data should go in output_buf and do the IDCT thing.
174       * We skip dummy blocks at the right and bottom edges (but blkn gets
175       * incremented past them!).  Note the inner loop relies on having
176       * allocated the MCU_buffer[] blocks sequentially.
177       */
178      blkn = 0;                 /* index of current DCT block within MCU */
179      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
180        compptr = cinfo->cur_comp_info[ci];
181        /* Don't bother to IDCT an uninteresting component. */
182        if (! compptr->component_needed) {
183          blkn += compptr->MCU_blocks;
184          continue;
185        }
186        inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
187        useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
188                                                    : compptr->last_col_width;
189        output_ptr = output_buf[compptr->component_index] +
190          yoffset * compptr->DCT_scaled_size;
191        start_col = MCU_col_num * compptr->MCU_sample_width;
192        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
193          if (cinfo->input_iMCU_row < last_iMCU_row ||
194              yoffset+yindex < compptr->last_row_height) {
195            output_col = start_col;
196            for (xindex = 0; xindex < useful_width; xindex++) {
197              (*inverse_DCT) (cinfo, compptr,
198                              (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
199                              output_ptr, output_col);
200              output_col += compptr->DCT_scaled_size;
201            }
202          }
203          blkn += compptr->MCU_width;
204          output_ptr += compptr->DCT_scaled_size;
205        }
206      }
207    }
208    /* Completed an MCU row, but perhaps not an iMCU row */
209    coef->MCU_ctr = 0;
210  }
211  /* Completed the iMCU row, advance counters for next one */
212  cinfo->output_iMCU_row++;
213  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
214    start_iMCU_row(cinfo);
215    return JPEG_ROW_COMPLETED;
216  }
217  /* Completed the scan */
218  (*cinfo->inputctl->finish_input_pass) (cinfo);
219  return JPEG_SCAN_COMPLETED;
220}
221
222
223/*
224 * Dummy consume-input routine for single-pass operation.
225 */
226
227METHODDEF(int)
228dummy_consume_data (j_decompress_ptr cinfo)
229{
230  return JPEG_SUSPENDED;        /* Always indicate nothing was done */
231}
232
233
234#ifdef D_MULTISCAN_FILES_SUPPORTED
235
236/*
237 * Consume input data and store it in the full-image coefficient buffer.
238 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
239 * ie, v_samp_factor block rows for each component in the scan.
240 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
241 */
242
243METHODDEF(int)
244consume_data (j_decompress_ptr cinfo)
245{
246  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
247  JDIMENSION MCU_col_num;       /* index of current MCU within row */
248  int blkn, ci, xindex, yindex, yoffset;
249  JDIMENSION start_col;
250  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
251  JBLOCKROW buffer_ptr;
252  jpeg_component_info *compptr;
253
254  /* Align the virtual buffers for the components used in this scan. */
255  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
256    compptr = cinfo->cur_comp_info[ci];
257    buffer[ci] = (*cinfo->mem->access_virt_barray)
258      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
259       cinfo->input_iMCU_row * compptr->v_samp_factor,
260       (JDIMENSION) compptr->v_samp_factor, TRUE);
261    /* Note: entropy decoder expects buffer to be zeroed,
262     * but this is handled automatically by the memory manager
263     * because we requested a pre-zeroed array.
264     */
265  }
266
267  /* Loop to process one whole iMCU row */
268  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
269       yoffset++) {
270    for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
271         MCU_col_num++) {
272      /* Construct list of pointers to DCT blocks belonging to this MCU */
273      blkn = 0;                 /* index of current DCT block within MCU */
274      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
275        compptr = cinfo->cur_comp_info[ci];
276        start_col = MCU_col_num * compptr->MCU_width;
277        for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
278          buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
279          for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
280            coef->MCU_buffer[blkn++] = buffer_ptr++;
281          }
282        }
283      }
284      /* Try to fetch the MCU. */
285      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
286        /* Suspension forced; update state counters and exit */
287        coef->MCU_vert_offset = yoffset;
288        coef->MCU_ctr = MCU_col_num;
289        return JPEG_SUSPENDED;
290      }
291    }
292    /* Completed an MCU row, but perhaps not an iMCU row */
293    coef->MCU_ctr = 0;
294  }
295  /* Completed the iMCU row, advance counters for next one */
296  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
297    start_iMCU_row(cinfo);
298    return JPEG_ROW_COMPLETED;
299  }
300  /* Completed the scan */
301  (*cinfo->inputctl->finish_input_pass) (cinfo);
302  return JPEG_SCAN_COMPLETED;
303}
304
305
306/*
307 * Decompress and return some data in the multi-pass case.
308 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
309 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
310 *
311 * NB: output_buf contains a plane for each component in image.
312 */
313
314METHODDEF(int)
315decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
316{
317  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
318  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
319  JDIMENSION block_num;
320  int ci, block_row, block_rows;
321  JBLOCKARRAY buffer;
322  JBLOCKROW buffer_ptr;
323  JSAMPARRAY output_ptr;
324  JDIMENSION output_col;
325  jpeg_component_info *compptr;
326  inverse_DCT_method_ptr inverse_DCT;
327
328  /* Force some input to be done if we are getting ahead of the input. */
329  while (cinfo->input_scan_number < cinfo->output_scan_number ||
330         (cinfo->input_scan_number == cinfo->output_scan_number &&
331          cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
332    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
333      return JPEG_SUSPENDED;
334  }
335
336  /* OK, output from the virtual arrays. */
337  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
338       ci++, compptr++) {
339    /* Don't bother to IDCT an uninteresting component. */
340    if (! compptr->component_needed)
341      continue;
342    /* Align the virtual buffer for this component. */
343    buffer = (*cinfo->mem->access_virt_barray)
344      ((j_common_ptr) cinfo, coef->whole_image[ci],
345       cinfo->output_iMCU_row * compptr->v_samp_factor,
346       (JDIMENSION) compptr->v_samp_factor, FALSE);
347    /* Count non-dummy DCT block rows in this iMCU row. */
348    if (cinfo->output_iMCU_row < last_iMCU_row)
349      block_rows = compptr->v_samp_factor;
350    else {
351      /* NB: can't use last_row_height here; it is input-side-dependent! */
352      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
353      if (block_rows == 0) block_rows = compptr->v_samp_factor;
354    }
355    inverse_DCT = cinfo->idct->inverse_DCT[ci];
356    output_ptr = output_buf[ci];
357    /* Loop over all DCT blocks to be processed. */
358    for (block_row = 0; block_row < block_rows; block_row++) {
359      buffer_ptr = buffer[block_row];
360      output_col = 0;
361      for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
362        (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
363                        output_ptr, output_col);
364        buffer_ptr++;
365        output_col += compptr->DCT_scaled_size;
366      }
367      output_ptr += compptr->DCT_scaled_size;
368    }
369  }
370
371  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
372    return JPEG_ROW_COMPLETED;
373  return JPEG_SCAN_COMPLETED;
374}
375
376#endif /* D_MULTISCAN_FILES_SUPPORTED */
377
378
379#ifdef BLOCK_SMOOTHING_SUPPORTED
380
381/*
382 * This code applies interblock smoothing as described by section K.8
383 * of the JPEG standard: the first 5 AC coefficients are estimated from
384 * the DC values of a DCT block and its 8 neighboring blocks.
385 * We apply smoothing only for progressive JPEG decoding, and only if
386 * the coefficients it can estimate are not yet known to full precision.
387 */
388
389/* Natural-order array positions of the first 5 zigzag-order coefficients */
390#define Q01_POS  1
391#define Q10_POS  8
392#define Q20_POS  16
393#define Q11_POS  9
394#define Q02_POS  2
395
396/*
397 * Determine whether block smoothing is applicable and safe.
398 * We also latch the current states of the coef_bits[] entries for the
399 * AC coefficients; otherwise, if the input side of the decompressor
400 * advances into a new scan, we might think the coefficients are known
401 * more accurately than they really are.
402 */
403
404LOCAL(boolean)
405smoothing_ok (j_decompress_ptr cinfo)
406{
407  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
408  boolean smoothing_useful = FALSE;
409  int ci, coefi;
410  jpeg_component_info *compptr;
411  JQUANT_TBL * qtable;
412  int * coef_bits;
413  int * coef_bits_latch;
414
415  if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
416    return FALSE;
417
418  /* Allocate latch area if not already done */
419  if (coef->coef_bits_latch == NULL)
420    coef->coef_bits_latch = (int *)
421      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
422                                  cinfo->num_components *
423                                  (SAVED_COEFS * SIZEOF(int)));
424  coef_bits_latch = coef->coef_bits_latch;
425
426  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
427       ci++, compptr++) {
428    /* All components' quantization values must already be latched. */
429    if ((qtable = compptr->quant_table) == NULL)
430      return FALSE;
431    /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
432    if (qtable->quantval[0] == 0 ||
433        qtable->quantval[Q01_POS] == 0 ||
434        qtable->quantval[Q10_POS] == 0 ||
435        qtable->quantval[Q20_POS] == 0 ||
436        qtable->quantval[Q11_POS] == 0 ||
437        qtable->quantval[Q02_POS] == 0)
438      return FALSE;
439    /* DC values must be at least partly known for all components. */
440    coef_bits = cinfo->coef_bits[ci];
441    if (coef_bits[0] < 0)
442      return FALSE;
443    /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
444    for (coefi = 1; coefi <= 5; coefi++) {
445      coef_bits_latch[coefi] = coef_bits[coefi];
446      if (coef_bits[coefi] != 0)
447        smoothing_useful = TRUE;
448    }
449    coef_bits_latch += SAVED_COEFS;
450  }
451
452  return smoothing_useful;
453}
454
455
456/*
457 * Variant of decompress_data for use when doing block smoothing.
458 */
459
460METHODDEF(int)
461decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
462{
463  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
464  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
465  JDIMENSION block_num, last_block_column;
466  int ci, block_row, block_rows, access_rows;
467  JBLOCKARRAY buffer;
468  JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
469  JSAMPARRAY output_ptr;
470  JDIMENSION output_col;
471  jpeg_component_info *compptr;
472  inverse_DCT_method_ptr inverse_DCT;
473  boolean first_row, last_row;
474  JBLOCK workspace;
475  int *coef_bits;
476  JQUANT_TBL *quanttbl;
477  INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
478  int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
479  int Al, pred;
480
481  /* Force some input to be done if we are getting ahead of the input. */
482  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
483         ! cinfo->inputctl->eoi_reached) {
484    if (cinfo->input_scan_number == cinfo->output_scan_number) {
485      /* If input is working on current scan, we ordinarily want it to
486       * have completed the current row.  But if input scan is DC,
487       * we want it to keep one row ahead so that next block row's DC
488       * values are up to date.
489       */
490      JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
491      if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
492        break;
493    }
494    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
495      return JPEG_SUSPENDED;
496  }
497
498  /* OK, output from the virtual arrays. */
499  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
500       ci++, compptr++) {
501    /* Don't bother to IDCT an uninteresting component. */
502    if (! compptr->component_needed)
503      continue;
504    /* Count non-dummy DCT block rows in this iMCU row. */
505    if (cinfo->output_iMCU_row < last_iMCU_row) {
506      block_rows = compptr->v_samp_factor;
507      access_rows = block_rows * 2; /* this and next iMCU row */
508      last_row = FALSE;
509    } else {
510      /* NB: can't use last_row_height here; it is input-side-dependent! */
511      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
512      if (block_rows == 0) block_rows = compptr->v_samp_factor;
513      access_rows = block_rows; /* this iMCU row only */
514      last_row = TRUE;
515    }
516    /* Align the virtual buffer for this component. */
517    if (cinfo->output_iMCU_row > 0) {
518      access_rows += compptr->v_samp_factor; /* prior iMCU row too */
519      buffer = (*cinfo->mem->access_virt_barray)
520        ((j_common_ptr) cinfo, coef->whole_image[ci],
521         (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
522         (JDIMENSION) access_rows, FALSE);
523      buffer += compptr->v_samp_factor; /* point to current iMCU row */
524      first_row = FALSE;
525    } else {
526      buffer = (*cinfo->mem->access_virt_barray)
527        ((j_common_ptr) cinfo, coef->whole_image[ci],
528         (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
529      first_row = TRUE;
530    }
531    /* Fetch component-dependent info */
532    coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
533    quanttbl = compptr->quant_table;
534    Q00 = quanttbl->quantval[0];
535    Q01 = quanttbl->quantval[Q01_POS];
536    Q10 = quanttbl->quantval[Q10_POS];
537    Q20 = quanttbl->quantval[Q20_POS];
538    Q11 = quanttbl->quantval[Q11_POS];
539    Q02 = quanttbl->quantval[Q02_POS];
540    inverse_DCT = cinfo->idct->inverse_DCT[ci];
541    output_ptr = output_buf[ci];
542    /* Loop over all DCT blocks to be processed. */
543    for (block_row = 0; block_row < block_rows; block_row++) {
544      buffer_ptr = buffer[block_row];
545      if (first_row && block_row == 0)
546        prev_block_row = buffer_ptr;
547      else
548        prev_block_row = buffer[block_row-1];
549      if (last_row && block_row == block_rows-1)
550        next_block_row = buffer_ptr;
551      else
552        next_block_row = buffer[block_row+1];
553      /* We fetch the surrounding DC values using a sliding-register approach.
554       * Initialize all nine here so as to do the right thing on narrow pics.
555       */
556      DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
557      DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
558      DC7 = DC8 = DC9 = (int) next_block_row[0][0];
559      output_col = 0;
560      last_block_column = compptr->width_in_blocks - 1;
561      for (block_num = 0; block_num <= last_block_column; block_num++) {
562        /* Fetch current DCT block into workspace so we can modify it. */
563        jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
564        /* Update DC values */
565        if (block_num < last_block_column) {
566          DC3 = (int) prev_block_row[1][0];
567          DC6 = (int) buffer_ptr[1][0];
568          DC9 = (int) next_block_row[1][0];
569        }
570        /* Compute coefficient estimates per K.8.
571         * An estimate is applied only if coefficient is still zero,
572         * and is not known to be fully accurate.
573         */
574        /* AC01 */
575        if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
576          num = 36 * Q00 * (DC4 - DC6);
577          if (num >= 0) {
578            pred = (int) (((Q01<<7) + num) / (Q01<<8));
579            if (Al > 0 && pred >= (1<<Al))
580              pred = (1<<Al)-1;
581          } else {
582            pred = (int) (((Q01<<7) - num) / (Q01<<8));
583            if (Al > 0 && pred >= (1<<Al))
584              pred = (1<<Al)-1;
585            pred = -pred;
586          }
587          workspace[1] = (JCOEF) pred;
588        }
589        /* AC10 */
590        if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
591          num = 36 * Q00 * (DC2 - DC8);
592          if (num >= 0) {
593            pred = (int) (((Q10<<7) + num) / (Q10<<8));
594            if (Al > 0 && pred >= (1<<Al))
595              pred = (1<<Al)-1;
596          } else {
597            pred = (int) (((Q10<<7) - num) / (Q10<<8));
598            if (Al > 0 && pred >= (1<<Al))
599              pred = (1<<Al)-1;
600            pred = -pred;
601          }
602          workspace[8] = (JCOEF) pred;
603        }
604        /* AC20 */
605        if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
606          num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
607          if (num >= 0) {
608            pred = (int) (((Q20<<7) + num) / (Q20<<8));
609            if (Al > 0 && pred >= (1<<Al))
610              pred = (1<<Al)-1;
611          } else {
612            pred = (int) (((Q20<<7) - num) / (Q20<<8));
613            if (Al > 0 && pred >= (1<<Al))
614              pred = (1<<Al)-1;
615            pred = -pred;
616          }
617          workspace[16] = (JCOEF) pred;
618        }
619        /* AC11 */
620        if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
621          num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
622          if (num >= 0) {
623            pred = (int) (((Q11<<7) + num) / (Q11<<8));
624            if (Al > 0 && pred >= (1<<Al))
625              pred = (1<<Al)-1;
626          } else {
627            pred = (int) (((Q11<<7) - num) / (Q11<<8));
628            if (Al > 0 && pred >= (1<<Al))
629              pred = (1<<Al)-1;
630            pred = -pred;
631          }
632          workspace[9] = (JCOEF) pred;
633        }
634        /* AC02 */
635        if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
636          num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
637          if (num >= 0) {
638            pred = (int) (((Q02<<7) + num) / (Q02<<8));
639            if (Al > 0 && pred >= (1<<Al))
640              pred = (1<<Al)-1;
641          } else {
642            pred = (int) (((Q02<<7) - num) / (Q02<<8));
643            if (Al > 0 && pred >= (1<<Al))
644              pred = (1<<Al)-1;
645            pred = -pred;
646          }
647          workspace[2] = (JCOEF) pred;
648        }
649        /* OK, do the IDCT */
650        (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
651                        output_ptr, output_col);
652        /* Advance for next column */
653        DC1 = DC2; DC2 = DC3;
654        DC4 = DC5; DC5 = DC6;
655        DC7 = DC8; DC8 = DC9;
656        buffer_ptr++, prev_block_row++, next_block_row++;
657        output_col += compptr->DCT_scaled_size;
658      }
659      output_ptr += compptr->DCT_scaled_size;
660    }
661  }
662
663  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
664    return JPEG_ROW_COMPLETED;
665  return JPEG_SCAN_COMPLETED;
666}
667
668#endif /* BLOCK_SMOOTHING_SUPPORTED */
669
670
671/*
672 * Initialize coefficient buffer controller.
673 */
674
675GLOBAL(void)
676jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
677{
678  my_coef_ptr coef;
679
680  coef = (my_coef_ptr)
681    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
682                                SIZEOF(my_coef_controller));
683  cinfo->coef = (struct jpeg_d_coef_controller *) coef;
684  coef->pub.start_input_pass = start_input_pass;
685  coef->pub.start_output_pass = start_output_pass;
686#ifdef BLOCK_SMOOTHING_SUPPORTED
687  coef->coef_bits_latch = NULL;
688#endif
689
690  /* Create the coefficient buffer. */
691  if (need_full_buffer) {
692#ifdef D_MULTISCAN_FILES_SUPPORTED
693    /* Allocate a full-image virtual array for each component, */
694    /* padded to a multiple of samp_factor DCT blocks in each direction. */
695    /* Note we ask for a pre-zeroed array. */
696    int ci, access_rows;
697    jpeg_component_info *compptr;
698
699    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
700         ci++, compptr++) {
701      access_rows = compptr->v_samp_factor;
702#ifdef BLOCK_SMOOTHING_SUPPORTED
703      /* If block smoothing could be used, need a bigger window */
704      if (cinfo->progressive_mode)
705        access_rows *= 3;
706#endif
707      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
708        ((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
709         (JDIMENSION) jround_up((long) compptr->width_in_blocks,
710                                (long) compptr->h_samp_factor),
711         (JDIMENSION) jround_up((long) compptr->height_in_blocks,
712                                (long) compptr->v_samp_factor),
713         (JDIMENSION) access_rows);
714    }
715    coef->pub.consume_data = consume_data;
716    coef->pub.decompress_data = decompress_data;
717    coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
718#else
719    ERREXIT(cinfo, JERR_NOT_COMPILED);
720#endif
721  } else {
722    /* We only need a single-MCU buffer. */
723    JBLOCKROW buffer;
724    int i;
725
726    buffer = (JBLOCKROW)
727      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
728                                  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
729    for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
730      coef->MCU_buffer[i] = buffer + i;
731    }
732    coef->pub.consume_data = dummy_consume_data;
733    coef->pub.decompress_data = decompress_onepass;
734    coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
735  }
736}
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