source: trunk/libjpeg/jdmainct.c @ 15

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

needed libs update

File size: 20.4 KB
Line 
1/*
2 * jdmainct.c
3 *
4 * Copyright (C) 1994-1996, 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 main buffer controller for decompression.
9 * The main buffer lies between the JPEG decompressor proper and the
10 * post-processor; it holds downsampled data in the JPEG colorspace.
11 *
12 * Note that this code is bypassed in raw-data mode, since the application
13 * supplies the equivalent of the main buffer in that case.
14 */
15
16#define JPEG_INTERNALS
17#include "jinclude.h"
18#include "jpeglib.h"
19
20
21/*
22 * In the current system design, the main buffer need never be a full-image
23 * buffer; any full-height buffers will be found inside the coefficient or
24 * postprocessing controllers.  Nonetheless, the main controller is not
25 * trivial.  Its responsibility is to provide context rows for upsampling/
26 * rescaling, and doing this in an efficient fashion is a bit tricky.
27 *
28 * Postprocessor input data is counted in "row groups".  A row group
29 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
30 * sample rows of each component.  (We require DCT_scaled_size values to be
31 * chosen such that these numbers are integers.  In practice DCT_scaled_size
32 * values will likely be powers of two, so we actually have the stronger
33 * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
34 * Upsampling will typically produce max_v_samp_factor pixel rows from each
35 * row group (times any additional scale factor that the upsampler is
36 * applying).
37 *
38 * The coefficient controller will deliver data to us one iMCU row at a time;
39 * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
40 * exactly min_DCT_scaled_size row groups.  (This amount of data corresponds
41 * to one row of MCUs when the image is fully interleaved.)  Note that the
42 * number of sample rows varies across components, but the number of row
43 * groups does not.  Some garbage sample rows may be included in the last iMCU
44 * row at the bottom of the image.
45 *
46 * Depending on the vertical scaling algorithm used, the upsampler may need
47 * access to the sample row(s) above and below its current input row group.
48 * The upsampler is required to set need_context_rows TRUE at global selection
49 * time if so.  When need_context_rows is FALSE, this controller can simply
50 * obtain one iMCU row at a time from the coefficient controller and dole it
51 * out as row groups to the postprocessor.
52 *
53 * When need_context_rows is TRUE, this controller guarantees that the buffer
54 * passed to postprocessing contains at least one row group's worth of samples
55 * above and below the row group(s) being processed.  Note that the context
56 * rows "above" the first passed row group appear at negative row offsets in
57 * the passed buffer.  At the top and bottom of the image, the required
58 * context rows are manufactured by duplicating the first or last real sample
59 * row; this avoids having special cases in the upsampling inner loops.
60 *
61 * The amount of context is fixed at one row group just because that's a
62 * convenient number for this controller to work with.  The existing
63 * upsamplers really only need one sample row of context.  An upsampler
64 * supporting arbitrary output rescaling might wish for more than one row
65 * group of context when shrinking the image; tough, we don't handle that.
66 * (This is justified by the assumption that downsizing will be handled mostly
67 * by adjusting the DCT_scaled_size values, so that the actual scale factor at
68 * the upsample step needn't be much less than one.)
69 *
70 * To provide the desired context, we have to retain the last two row groups
71 * of one iMCU row while reading in the next iMCU row.  (The last row group
72 * can't be processed until we have another row group for its below-context,
73 * and so we have to save the next-to-last group too for its above-context.)
74 * We could do this most simply by copying data around in our buffer, but
75 * that'd be very slow.  We can avoid copying any data by creating a rather
76 * strange pointer structure.  Here's how it works.  We allocate a workspace
77 * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
78 * of row groups per iMCU row).  We create two sets of redundant pointers to
79 * the workspace.  Labeling the physical row groups 0 to M+1, the synthesized
80 * pointer lists look like this:
81 *                   M+1                          M-1
82 * master pointer --> 0         master pointer --> 0
83 *                    1                            1
84 *                   ...                          ...
85 *                   M-3                          M-3
86 *                   M-2                           M
87 *                   M-1                          M+1
88 *                    M                           M-2
89 *                   M+1                          M-1
90 *                    0                            0
91 * We read alternate iMCU rows using each master pointer; thus the last two
92 * row groups of the previous iMCU row remain un-overwritten in the workspace.
93 * The pointer lists are set up so that the required context rows appear to
94 * be adjacent to the proper places when we pass the pointer lists to the
95 * upsampler.
96 *
97 * The above pictures describe the normal state of the pointer lists.
98 * At top and bottom of the image, we diddle the pointer lists to duplicate
99 * the first or last sample row as necessary (this is cheaper than copying
100 * sample rows around).
101 *
102 * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1.  In that
103 * situation each iMCU row provides only one row group so the buffering logic
104 * must be different (eg, we must read two iMCU rows before we can emit the
105 * first row group).  For now, we simply do not support providing context
106 * rows when min_DCT_scaled_size is 1.  That combination seems unlikely to
107 * be worth providing --- if someone wants a 1/8th-size preview, they probably
108 * want it quick and dirty, so a context-free upsampler is sufficient.
109 */
110
111
112/* Private buffer controller object */
113
114typedef struct {
115  struct jpeg_d_main_controller pub; /* public fields */
116
117  /* Pointer to allocated workspace (M or M+2 row groups). */
118  JSAMPARRAY buffer[MAX_COMPONENTS];
119
120  boolean buffer_full;          /* Have we gotten an iMCU row from decoder? */
121  JDIMENSION rowgroup_ctr;      /* counts row groups output to postprocessor */
122
123  /* Remaining fields are only used in the context case. */
124
125  /* These are the master pointers to the funny-order pointer lists. */
126  JSAMPIMAGE xbuffer[2];        /* pointers to weird pointer lists */
127
128  int whichptr;                 /* indicates which pointer set is now in use */
129  int context_state;            /* process_data state machine status */
130  JDIMENSION rowgroups_avail;   /* row groups available to postprocessor */
131  JDIMENSION iMCU_row_ctr;      /* counts iMCU rows to detect image top/bot */
132} my_main_controller;
133
134typedef my_main_controller * my_main_ptr;
135
136/* context_state values: */
137#define CTX_PREPARE_FOR_IMCU    0       /* need to prepare for MCU row */
138#define CTX_PROCESS_IMCU        1       /* feeding iMCU to postprocessor */
139#define CTX_POSTPONED_ROW       2       /* feeding postponed row group */
140
141
142/* Forward declarations */
143METHODDEF(void) process_data_simple_main
144        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
145             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
146METHODDEF(void) process_data_context_main
147        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
148             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
149#ifdef QUANT_2PASS_SUPPORTED
150METHODDEF(void) process_data_crank_post
151        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
152             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
153#endif
154
155
156LOCAL(void)
157alloc_funny_pointers (j_decompress_ptr cinfo)
158/* Allocate space for the funny pointer lists.
159 * This is done only once, not once per pass.
160 */
161{
162  my_main_ptr main = (my_main_ptr) cinfo->main;
163  int ci, rgroup;
164  int M = cinfo->min_DCT_scaled_size;
165  jpeg_component_info *compptr;
166  JSAMPARRAY xbuf;
167
168  /* Get top-level space for component array pointers.
169   * We alloc both arrays with one call to save a few cycles.
170   */
171  main->xbuffer[0] = (JSAMPIMAGE)
172    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
173                                cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
174  main->xbuffer[1] = main->xbuffer[0] + cinfo->num_components;
175
176  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
177       ci++, compptr++) {
178    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
179      cinfo->min_DCT_scaled_size; /* height of a row group of component */
180    /* Get space for pointer lists --- M+4 row groups in each list.
181     * We alloc both pointer lists with one call to save a few cycles.
182     */
183    xbuf = (JSAMPARRAY)
184      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
185                                  2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
186    xbuf += rgroup;             /* want one row group at negative offsets */
187    main->xbuffer[0][ci] = xbuf;
188    xbuf += rgroup * (M + 4);
189    main->xbuffer[1][ci] = xbuf;
190  }
191}
192
193
194LOCAL(void)
195make_funny_pointers (j_decompress_ptr cinfo)
196/* Create the funny pointer lists discussed in the comments above.
197 * The actual workspace is already allocated (in main->buffer),
198 * and the space for the pointer lists is allocated too.
199 * This routine just fills in the curiously ordered lists.
200 * This will be repeated at the beginning of each pass.
201 */
202{
203  my_main_ptr main = (my_main_ptr) cinfo->main;
204  int ci, i, rgroup;
205  int M = cinfo->min_DCT_scaled_size;
206  jpeg_component_info *compptr;
207  JSAMPARRAY buf, xbuf0, xbuf1;
208
209  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
210       ci++, compptr++) {
211    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
212      cinfo->min_DCT_scaled_size; /* height of a row group of component */
213    xbuf0 = main->xbuffer[0][ci];
214    xbuf1 = main->xbuffer[1][ci];
215    /* First copy the workspace pointers as-is */
216    buf = main->buffer[ci];
217    for (i = 0; i < rgroup * (M + 2); i++) {
218      xbuf0[i] = xbuf1[i] = buf[i];
219    }
220    /* In the second list, put the last four row groups in swapped order */
221    for (i = 0; i < rgroup * 2; i++) {
222      xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
223      xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
224    }
225    /* The wraparound pointers at top and bottom will be filled later
226     * (see set_wraparound_pointers, below).  Initially we want the "above"
227     * pointers to duplicate the first actual data line.  This only needs
228     * to happen in xbuffer[0].
229     */
230    for (i = 0; i < rgroup; i++) {
231      xbuf0[i - rgroup] = xbuf0[0];
232    }
233  }
234}
235
236
237LOCAL(void)
238set_wraparound_pointers (j_decompress_ptr cinfo)
239/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
240 * This changes the pointer list state from top-of-image to the normal state.
241 */
242{
243  my_main_ptr main = (my_main_ptr) cinfo->main;
244  int ci, i, rgroup;
245  int M = cinfo->min_DCT_scaled_size;
246  jpeg_component_info *compptr;
247  JSAMPARRAY xbuf0, xbuf1;
248
249  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
250       ci++, compptr++) {
251    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
252      cinfo->min_DCT_scaled_size; /* height of a row group of component */
253    xbuf0 = main->xbuffer[0][ci];
254    xbuf1 = main->xbuffer[1][ci];
255    for (i = 0; i < rgroup; i++) {
256      xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
257      xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
258      xbuf0[rgroup*(M+2) + i] = xbuf0[i];
259      xbuf1[rgroup*(M+2) + i] = xbuf1[i];
260    }
261  }
262}
263
264
265LOCAL(void)
266set_bottom_pointers (j_decompress_ptr cinfo)
267/* Change the pointer lists to duplicate the last sample row at the bottom
268 * of the image.  whichptr indicates which xbuffer holds the final iMCU row.
269 * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
270 */
271{
272  my_main_ptr main = (my_main_ptr) cinfo->main;
273  int ci, i, rgroup, iMCUheight, rows_left;
274  jpeg_component_info *compptr;
275  JSAMPARRAY xbuf;
276
277  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
278       ci++, compptr++) {
279    /* Count sample rows in one iMCU row and in one row group */
280    iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
281    rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
282    /* Count nondummy sample rows remaining for this component */
283    rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
284    if (rows_left == 0) rows_left = iMCUheight;
285    /* Count nondummy row groups.  Should get same answer for each component,
286     * so we need only do it once.
287     */
288    if (ci == 0) {
289      main->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
290    }
291    /* Duplicate the last real sample row rgroup*2 times; this pads out the
292     * last partial rowgroup and ensures at least one full rowgroup of context.
293     */
294    xbuf = main->xbuffer[main->whichptr][ci];
295    for (i = 0; i < rgroup * 2; i++) {
296      xbuf[rows_left + i] = xbuf[rows_left-1];
297    }
298  }
299}
300
301
302/*
303 * Initialize for a processing pass.
304 */
305
306METHODDEF(void)
307start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
308{
309  my_main_ptr main = (my_main_ptr) cinfo->main;
310
311  switch (pass_mode) {
312  case JBUF_PASS_THRU:
313    if (cinfo->upsample->need_context_rows) {
314      main->pub.process_data = process_data_context_main;
315      make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
316      main->whichptr = 0;       /* Read first iMCU row into xbuffer[0] */
317      main->context_state = CTX_PREPARE_FOR_IMCU;
318      main->iMCU_row_ctr = 0;
319    } else {
320      /* Simple case with no context needed */
321      main->pub.process_data = process_data_simple_main;
322    }
323    main->buffer_full = FALSE;  /* Mark buffer empty */
324    main->rowgroup_ctr = 0;
325    break;
326#ifdef QUANT_2PASS_SUPPORTED
327  case JBUF_CRANK_DEST:
328    /* For last pass of 2-pass quantization, just crank the postprocessor */
329    main->pub.process_data = process_data_crank_post;
330    break;
331#endif
332  default:
333    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
334    break;
335  }
336}
337
338
339/*
340 * Process some data.
341 * This handles the simple case where no context is required.
342 */
343
344METHODDEF(void)
345process_data_simple_main (j_decompress_ptr cinfo,
346                          JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
347                          JDIMENSION out_rows_avail)
348{
349  my_main_ptr main = (my_main_ptr) cinfo->main;
350  JDIMENSION rowgroups_avail;
351
352  /* Read input data if we haven't filled the main buffer yet */
353  if (! main->buffer_full) {
354    if (! (*cinfo->coef->decompress_data) (cinfo, main->buffer))
355      return;                   /* suspension forced, can do nothing more */
356    main->buffer_full = TRUE;   /* OK, we have an iMCU row to work with */
357  }
358
359  /* There are always min_DCT_scaled_size row groups in an iMCU row. */
360  rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size;
361  /* Note: at the bottom of the image, we may pass extra garbage row groups
362   * to the postprocessor.  The postprocessor has to check for bottom
363   * of image anyway (at row resolution), so no point in us doing it too.
364   */
365
366  /* Feed the postprocessor */
367  (*cinfo->post->post_process_data) (cinfo, main->buffer,
368                                     &main->rowgroup_ctr, rowgroups_avail,
369                                     output_buf, out_row_ctr, out_rows_avail);
370
371  /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
372  if (main->rowgroup_ctr >= rowgroups_avail) {
373    main->buffer_full = FALSE;
374    main->rowgroup_ctr = 0;
375  }
376}
377
378
379/*
380 * Process some data.
381 * This handles the case where context rows must be provided.
382 */
383
384METHODDEF(void)
385process_data_context_main (j_decompress_ptr cinfo,
386                           JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
387                           JDIMENSION out_rows_avail)
388{
389  my_main_ptr main = (my_main_ptr) cinfo->main;
390
391  /* Read input data if we haven't filled the main buffer yet */
392  if (! main->buffer_full) {
393    if (! (*cinfo->coef->decompress_data) (cinfo,
394                                           main->xbuffer[main->whichptr]))
395      return;                   /* suspension forced, can do nothing more */
396    main->buffer_full = TRUE;   /* OK, we have an iMCU row to work with */
397    main->iMCU_row_ctr++;       /* count rows received */
398  }
399
400  /* Postprocessor typically will not swallow all the input data it is handed
401   * in one call (due to filling the output buffer first).  Must be prepared
402   * to exit and restart.  This switch lets us keep track of how far we got.
403   * Note that each case falls through to the next on successful completion.
404   */
405  switch (main->context_state) {
406  case CTX_POSTPONED_ROW:
407    /* Call postprocessor using previously set pointers for postponed row */
408    (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
409                        &main->rowgroup_ctr, main->rowgroups_avail,
410                        output_buf, out_row_ctr, out_rows_avail);
411    if (main->rowgroup_ctr < main->rowgroups_avail)
412      return;                   /* Need to suspend */
413    main->context_state = CTX_PREPARE_FOR_IMCU;
414    if (*out_row_ctr >= out_rows_avail)
415      return;                   /* Postprocessor exactly filled output buf */
416    /*FALLTHROUGH*/
417  case CTX_PREPARE_FOR_IMCU:
418    /* Prepare to process first M-1 row groups of this iMCU row */
419    main->rowgroup_ctr = 0;
420    main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1);
421    /* Check for bottom of image: if so, tweak pointers to "duplicate"
422     * the last sample row, and adjust rowgroups_avail to ignore padding rows.
423     */
424    if (main->iMCU_row_ctr == cinfo->total_iMCU_rows)
425      set_bottom_pointers(cinfo);
426    main->context_state = CTX_PROCESS_IMCU;
427    /*FALLTHROUGH*/
428  case CTX_PROCESS_IMCU:
429    /* Call postprocessor using previously set pointers */
430    (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
431                        &main->rowgroup_ctr, main->rowgroups_avail,
432                        output_buf, out_row_ctr, out_rows_avail);
433    if (main->rowgroup_ctr < main->rowgroups_avail)
434      return;                   /* Need to suspend */
435    /* After the first iMCU, change wraparound pointers to normal state */
436    if (main->iMCU_row_ctr == 1)
437      set_wraparound_pointers(cinfo);
438    /* Prepare to load new iMCU row using other xbuffer list */
439    main->whichptr ^= 1;        /* 0=>1 or 1=>0 */
440    main->buffer_full = FALSE;
441    /* Still need to process last row group of this iMCU row, */
442    /* which is saved at index M+1 of the other xbuffer */
443    main->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1);
444    main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2);
445    main->context_state = CTX_POSTPONED_ROW;
446  }
447}
448
449
450/*
451 * Process some data.
452 * Final pass of two-pass quantization: just call the postprocessor.
453 * Source data will be the postprocessor controller's internal buffer.
454 */
455
456#ifdef QUANT_2PASS_SUPPORTED
457
458METHODDEF(void)
459process_data_crank_post (j_decompress_ptr cinfo,
460                         JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
461                         JDIMENSION out_rows_avail)
462{
463  (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
464                                     (JDIMENSION *) NULL, (JDIMENSION) 0,
465                                     output_buf, out_row_ctr, out_rows_avail);
466}
467
468#endif /* QUANT_2PASS_SUPPORTED */
469
470
471/*
472 * Initialize main buffer controller.
473 */
474
475GLOBAL(void)
476jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
477{
478  my_main_ptr main;
479  int ci, rgroup, ngroups;
480  jpeg_component_info *compptr;
481
482  main = (my_main_ptr)
483    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
484                                SIZEOF(my_main_controller));
485  cinfo->main = (struct jpeg_d_main_controller *) main;
486  main->pub.start_pass = start_pass_main;
487
488  if (need_full_buffer)         /* shouldn't happen */
489    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
490
491  /* Allocate the workspace.
492   * ngroups is the number of row groups we need.
493   */
494  if (cinfo->upsample->need_context_rows) {
495    if (cinfo->min_DCT_scaled_size < 2) /* unsupported, see comments above */
496      ERREXIT(cinfo, JERR_NOTIMPL);
497    alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
498    ngroups = cinfo->min_DCT_scaled_size + 2;
499  } else {
500    ngroups = cinfo->min_DCT_scaled_size;
501  }
502
503  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
504       ci++, compptr++) {
505    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
506      cinfo->min_DCT_scaled_size; /* height of a row group of component */
507    main->buffer[ci] = (*cinfo->mem->alloc_sarray)
508                        ((j_common_ptr) cinfo, JPOOL_IMAGE,
509                         compptr->width_in_blocks * compptr->DCT_scaled_size,
510                         (JDIMENSION) (rgroup * ngroups));
511  }
512}
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