source: golgotha/src/i4/loaders/jpg/jdmainct.cc @ 80

Last change on this file since 80 was 80, checked in by Sam Hocevar, 12 years ago
  • Adding the Golgotha source code. Not sure what's going to be interesting in there, but since it's all public domain, there's certainly stuff to pick up.
File size: 20.9 KB
Line 
1/********************************************************************** <BR>
2  This file is part of Crack dot Com's free source code release of
3  Golgotha. <a href="http://www.crack.com/golgotha_release"> <BR> for
4  information about compiling & licensing issues visit this URL</a>
5  <PRE> If that doesn't help, contact Jonathan Clark at
6  golgotha_source@usa.net (Subject should have "GOLG" in it)
7***********************************************************************/
8
9/*
10 * jdmainct.c
11 *
12 * Copyright (C) 1994-1996, Thomas G. Lane.
13 * This file is part of the Independent JPEG Group's software.
14 * For conditions of distribution and use, see the accompanying README file.
15 *
16 * This file contains the main buffer controller for decompression.
17 * The main buffer lies between the JPEG decompressor proper and the
18 * post-processor; it holds downsampled data in the JPEG colorspace.
19 *
20 * Note that this code is bypassed in raw-data mode, since the application
21 * supplies the equivalent of the main buffer in that case.
22 */
23
24#define JPEG_INTERNALS
25#include "loaders/jpg/jinclude.h"
26#include "loaders/jpg/jpeglib.h"
27
28
29/*
30 * In the current system design, the main buffer need never be a full-image
31 * buffer; any full-height buffers will be found inside the coefficient or
32 * postprocessing controllers.  Nonetheless, the main controller is not
33 * trivial.  Its responsibility is to provide context rows for upsampling/
34 * rescaling, and doing this in an efficient fashion is a bit tricky.
35 *
36 * Postprocessor input data is counted in "row groups".  A row group
37 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
38 * sample rows of each component.  (We require DCT_scaled_size values to be
39 * chosen such that these numbers are integers.  In practice DCT_scaled_size
40 * values will likely be powers of two, so we actually have the stronger
41 * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
42 * Upsampling will typically produce max_v_samp_factor pixel rows from each
43 * row group (times any additional scale factor that the upsampler is
44 * applying).
45 *
46 * The coefficient controller will deliver data to us one iMCU row at a time;
47 * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
48 * exactly min_DCT_scaled_size row groups.  (This amount of data corresponds
49 * to one row of MCUs when the image is fully interleaved.)  Note that the
50 * number of sample rows varies across components, but the number of row
51 * groups does not.  Some garbage sample rows may be included in the last iMCU
52 * row at the bottom of the image.
53 *
54 * Depending on the vertical scaling algorithm used, the upsampler may need
55 * access to the sample row(s) above and below its current input row group.
56 * The upsampler is required to set need_context_rows TRUE at global selection
57 * time if so.  When need_context_rows is FALSE, this controller can simply
58 * obtain one iMCU row at a time from the coefficient controller and dole it
59 * out as row groups to the postprocessor.
60 *
61 * When need_context_rows is TRUE, this controller guarantees that the buffer
62 * passed to postprocessing contains at least one row group's worth of samples
63 * above and below the row group(s) being processed.  Note that the context
64 * rows "above" the first passed row group appear at negative row offsets in
65 * the passed buffer.  At the top and bottom of the image, the required
66 * context rows are manufactured by duplicating the first or last real sample
67 * row; this avoids having special cases in the upsampling inner loops.
68 *
69 * The amount of context is fixed at one row group just because that's a
70 * convenient number for this controller to work with.  The existing
71 * upsamplers really only need one sample row of context.  An upsampler
72 * supporting arbitrary output rescaling might wish for more than one row
73 * group of context when shrinking the image; tough, we don't handle that.
74 * (This is justified by the assumption that downsizing will be handled mostly
75 * by adjusting the DCT_scaled_size values, so that the actual scale factor at
76 * the upsample step needn't be much less than one.)
77 *
78 * To provide the desired context, we have to retain the last two row groups
79 * of one iMCU row while reading in the next iMCU row.  (The last row group
80 * can't be processed until we have another row group for its below-context,
81 * and so we have to save the next-to-last group too for its above-context.)
82 * We could do this most simply by copying data around in our buffer, but
83 * that'd be very slow.  We can avoid copying any data by creating a rather
84 * strange pointer structure.  Here's how it works.  We allocate a workspace
85 * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
86 * of row groups per iMCU row).  We create two sets of redundant pointers to
87 * the workspace.  Labeling the physical row groups 0 to M+1, the synthesized
88 * pointer lists look like this:
89 *                   M+1                          M-1
90 * master pointer --> 0         master pointer --> 0
91 *                    1                            1
92 *                   ...                          ...
93 *                   M-3                          M-3
94 *                   M-2                           M
95 *                   M-1                          M+1
96 *                    M                           M-2
97 *                   M+1                          M-1
98 *                    0                            0
99 * We read alternate iMCU rows using each master pointer; thus the last two
100 * row groups of the previous iMCU row remain un-overwritten in the workspace.
101 * The pointer lists are set up so that the required context rows appear to
102 * be adjacent to the proper places when we pass the pointer lists to the
103 * upsampler.
104 *
105 * The above pictures describe the normal state of the pointer lists.
106 * At top and bottom of the image, we diddle the pointer lists to duplicate
107 * the first or last sample row as necessary (this is cheaper than copying
108 * sample rows around).
109 *
110 * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1.  In that
111 * situation each iMCU row provides only one row group so the buffering logic
112 * must be different (eg, we must read two iMCU rows before we can emit the
113 * first row group).  For now, we simply do not support providing context
114 * rows when min_DCT_scaled_size is 1.  That combination seems unlikely to
115 * be worth providing --- if someone wants a 1/8th-size preview, they probably
116 * want it quick and dirty, so a context-free upsampler is sufficient.
117 */
118
119
120/* Private buffer controller object */
121
122typedef struct {
123  struct jpeg_d_main_controller pub; /* public fields */
124
125  /* Pointer to allocated workspace (M or M+2 row groups). */
126  JSAMPARRAY buffer[MAX_COMPONENTS];
127
128  boolean buffer_full;          /* Have we gotten an iMCU row from decoder? */
129  JDIMENSION rowgroup_ctr;      /* counts row groups output to postprocessor */
130
131  /* Remaining fields are only used in the context case. */
132
133  /* These are the master pointers to the funny-order pointer lists. */
134  JSAMPIMAGE xbuffer[2];        /* pointers to weird pointer lists */
135
136  int whichptr;                 /* indicates which pointer set is now in use */
137  int context_state;            /* process_data state machine status */
138  JDIMENSION rowgroups_avail;   /* row groups available to postprocessor */
139  JDIMENSION iMCU_row_ctr;      /* counts iMCU rows to detect image top/bot */
140} my_main_controller;
141
142typedef my_main_controller * my_main_ptr;
143
144/* context_state values: */
145#define CTX_PREPARE_FOR_IMCU    0       /* need to prepare for MCU row */
146#define CTX_PROCESS_IMCU        1       /* feeding iMCU to postprocessor */
147#define CTX_POSTPONED_ROW       2       /* feeding postponed row group */
148
149
150/* Forward declarations */
151METHODDEF(void) process_data_simple_main
152        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
153             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
154METHODDEF(void) process_data_context_main
155        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
156             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
157#ifdef QUANT_2PASS_SUPPORTED
158METHODDEF(void) process_data_crank_post
159        JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
160             JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
161#endif
162
163
164LOCAL(void)
165alloc_funny_pointers (j_decompress_ptr cinfo)
166/* Allocate space for the funny pointer lists.
167 * This is done only once, not once per pass.
168 */
169{
170  my_main_ptr main = (my_main_ptr) cinfo->main;
171  int ci, rgroup;
172  int M = cinfo->min_DCT_scaled_size;
173  jpeg_component_info *compptr;
174  JSAMPARRAY xbuf;
175
176  /* Get top-level space for component array pointers.
177   * We alloc both arrays with one call to save a few cycles.
178   */
179  main->xbuffer[0] = (JSAMPIMAGE)
180    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
181                                cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
182  main->xbuffer[1] = main->xbuffer[0] + cinfo->num_components;
183
184  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
185       ci++, compptr++) {
186    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
187      cinfo->min_DCT_scaled_size; /* height of a row group of component */
188    /* Get space for pointer lists --- M+4 row groups in each list.
189     * We alloc both pointer lists with one call to save a few cycles.
190     */
191    xbuf = (JSAMPARRAY)
192      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
193                                  2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
194    xbuf += rgroup;             /* want one row group at negative offsets */
195    main->xbuffer[0][ci] = xbuf;
196    xbuf += rgroup * (M + 4);
197    main->xbuffer[1][ci] = xbuf;
198  }
199}
200
201
202LOCAL(void)
203make_funny_pointers (j_decompress_ptr cinfo)
204/* Create the funny pointer lists discussed in the comments above.
205 * The actual workspace is already allocated (in main->buffer),
206 * and the space for the pointer lists is allocated too.
207 * This routine just fills in the curiously ordered lists.
208 * This will be repeated at the beginning of each pass.
209 */
210{
211  my_main_ptr main = (my_main_ptr) cinfo->main;
212  int ci, i, rgroup;
213  int M = cinfo->min_DCT_scaled_size;
214  jpeg_component_info *compptr;
215  JSAMPARRAY buf, xbuf0, xbuf1;
216
217  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
218       ci++, compptr++) {
219    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
220      cinfo->min_DCT_scaled_size; /* height of a row group of component */
221    xbuf0 = main->xbuffer[0][ci];
222    xbuf1 = main->xbuffer[1][ci];
223    /* First copy the workspace pointers as-is */
224    buf = main->buffer[ci];
225    for (i = 0; i < rgroup * (M + 2); i++) {
226      xbuf0[i] = xbuf1[i] = buf[i];
227    }
228    /* In the second list, put the last four row groups in swapped order */
229    for (i = 0; i < rgroup * 2; i++) {
230      xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
231      xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
232    }
233    /* The wraparound pointers at top and bottom will be filled later
234     * (see set_wraparound_pointers, below).  Initially we want the "above"
235     * pointers to duplicate the first actual data line.  This only needs
236     * to happen in xbuffer[0].
237     */
238    for (i = 0; i < rgroup; i++) {
239      xbuf0[i - rgroup] = xbuf0[0];
240    }
241  }
242}
243
244
245LOCAL(void)
246set_wraparound_pointers (j_decompress_ptr cinfo)
247/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
248 * This changes the pointer list state from top-of-image to the normal state.
249 */
250{
251  my_main_ptr main = (my_main_ptr) cinfo->main;
252  int ci, i, rgroup;
253  int M = cinfo->min_DCT_scaled_size;
254  jpeg_component_info *compptr;
255  JSAMPARRAY xbuf0, xbuf1;
256
257  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
258       ci++, compptr++) {
259    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
260      cinfo->min_DCT_scaled_size; /* height of a row group of component */
261    xbuf0 = main->xbuffer[0][ci];
262    xbuf1 = main->xbuffer[1][ci];
263    for (i = 0; i < rgroup; i++) {
264      xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
265      xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
266      xbuf0[rgroup*(M+2) + i] = xbuf0[i];
267      xbuf1[rgroup*(M+2) + i] = xbuf1[i];
268    }
269  }
270}
271
272
273LOCAL(void)
274set_bottom_pointers (j_decompress_ptr cinfo)
275/* Change the pointer lists to duplicate the last sample row at the bottom
276 * of the image.  whichptr indicates which xbuffer holds the final iMCU row.
277 * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
278 */
279{
280  my_main_ptr main = (my_main_ptr) cinfo->main;
281  int ci, i, rgroup, iMCUheight, rows_left;
282  jpeg_component_info *compptr;
283  JSAMPARRAY xbuf;
284
285  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
286       ci++, compptr++) {
287    /* Count sample rows in one iMCU row and in one row group */
288    iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
289    rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
290    /* Count nondummy sample rows remaining for this component */
291    rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
292    if (rows_left == 0) rows_left = iMCUheight;
293    /* Count nondummy row groups.  Should get same answer for each component,
294     * so we need only do it once.
295     */
296    if (ci == 0) {
297      main->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
298    }
299    /* Duplicate the last real sample row rgroup*2 times; this pads out the
300     * last partial rowgroup and ensures at least one full rowgroup of context.
301     */
302    xbuf = main->xbuffer[main->whichptr][ci];
303    for (i = 0; i < rgroup * 2; i++) {
304      xbuf[rows_left + i] = xbuf[rows_left-1];
305    }
306  }
307}
308
309
310/*
311 * Initialize for a processing pass.
312 */
313
314METHODDEF(void)
315start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
316{
317  my_main_ptr main = (my_main_ptr) cinfo->main;
318
319  switch (pass_mode) {
320  case JBUF_PASS_THRU:
321    if (cinfo->upsample->need_context_rows) {
322      main->pub.process_data = process_data_context_main;
323      make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
324      main->whichptr = 0;       /* Read first iMCU row into xbuffer[0] */
325      main->context_state = CTX_PREPARE_FOR_IMCU;
326      main->iMCU_row_ctr = 0;
327    } else {
328      /* Simple case with no context needed */
329      main->pub.process_data = process_data_simple_main;
330    }
331    main->buffer_full = FALSE;  /* Mark buffer empty */
332    main->rowgroup_ctr = 0;
333    break;
334#ifdef QUANT_2PASS_SUPPORTED
335  case JBUF_CRANK_DEST:
336    /* For last pass of 2-pass quantization, just crank the postprocessor */
337    main->pub.process_data = process_data_crank_post;
338    break;
339#endif
340  default:
341    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
342    break;
343  }
344}
345
346
347/*
348 * Process some data.
349 * This handles the simple case where no context is required.
350 */
351
352METHODDEF(void)
353process_data_simple_main (j_decompress_ptr cinfo,
354                          JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
355                          JDIMENSION out_rows_avail)
356{
357  my_main_ptr main = (my_main_ptr) cinfo->main;
358  JDIMENSION rowgroups_avail;
359
360  /* Read input data if we haven't filled the main buffer yet */
361  if (! main->buffer_full) {
362    if (! (*cinfo->coef->decompress_data) (cinfo, main->buffer))
363      return;                   /* suspension forced, can do nothing more */
364    main->buffer_full = TRUE;   /* OK, we have an iMCU row to work with */
365  }
366
367  /* There are always min_DCT_scaled_size row groups in an iMCU row. */
368  rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size;
369  /* Note: at the bottom of the image, we may pass extra garbage row groups
370   * to the postprocessor.  The postprocessor has to check for bottom
371   * of image anyway (at row resolution), so no point in us doing it too.
372   */
373
374  /* Feed the postprocessor */
375  (*cinfo->post->post_process_data) (cinfo, main->buffer,
376                                     &main->rowgroup_ctr, rowgroups_avail,
377                                     output_buf, out_row_ctr, out_rows_avail);
378
379  /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
380  if (main->rowgroup_ctr >= rowgroups_avail) {
381    main->buffer_full = FALSE;
382    main->rowgroup_ctr = 0;
383  }
384}
385
386
387/*
388 * Process some data.
389 * This handles the case where context rows must be provided.
390 */
391
392METHODDEF(void)
393process_data_context_main (j_decompress_ptr cinfo,
394                           JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
395                           JDIMENSION out_rows_avail)
396{
397  my_main_ptr main = (my_main_ptr) cinfo->main;
398
399  /* Read input data if we haven't filled the main buffer yet */
400  if (! main->buffer_full) {
401    if (! (*cinfo->coef->decompress_data) (cinfo,
402                                           main->xbuffer[main->whichptr]))
403      return;                   /* suspension forced, can do nothing more */
404    main->buffer_full = TRUE;   /* OK, we have an iMCU row to work with */
405    main->iMCU_row_ctr++;       /* count rows received */
406  }
407
408  /* Postprocessor typically will not swallow all the input data it is handed
409   * in one call (due to filling the output buffer first).  Must be prepared
410   * to exit and restart.  This switch lets us keep track of how far we got.
411   * Note that each case falls through to the next on successful completion.
412   */
413  switch (main->context_state) {
414  case CTX_POSTPONED_ROW:
415    /* Call postprocessor using previously set pointers for postponed row */
416    (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
417                        &main->rowgroup_ctr, main->rowgroups_avail,
418                        output_buf, out_row_ctr, out_rows_avail);
419    if (main->rowgroup_ctr < main->rowgroups_avail)
420      return;                   /* Need to suspend */
421    main->context_state = CTX_PREPARE_FOR_IMCU;
422    if (*out_row_ctr >= out_rows_avail)
423      return;                   /* Postprocessor exactly filled output buf */
424    /*FALLTHROUGH*/
425  case CTX_PREPARE_FOR_IMCU:
426    /* Prepare to process first M-1 row groups of this iMCU row */
427    main->rowgroup_ctr = 0;
428    main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1);
429    /* Check for bottom of image: if so, tweak pointers to "duplicate"
430     * the last sample row, and adjust rowgroups_avail to ignore padding rows.
431     */
432    if (main->iMCU_row_ctr == cinfo->total_iMCU_rows)
433      set_bottom_pointers(cinfo);
434    main->context_state = CTX_PROCESS_IMCU;
435    /*FALLTHROUGH*/
436  case CTX_PROCESS_IMCU:
437    /* Call postprocessor using previously set pointers */
438    (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
439                        &main->rowgroup_ctr, main->rowgroups_avail,
440                        output_buf, out_row_ctr, out_rows_avail);
441    if (main->rowgroup_ctr < main->rowgroups_avail)
442      return;                   /* Need to suspend */
443    /* After the first iMCU, change wraparound pointers to normal state */
444    if (main->iMCU_row_ctr == 1)
445      set_wraparound_pointers(cinfo);
446    /* Prepare to load new iMCU row using other xbuffer list */
447    main->whichptr ^= 1;        /* 0=>1 or 1=>0 */
448    main->buffer_full = FALSE;
449    /* Still need to process last row group of this iMCU row, */
450    /* which is saved at index M+1 of the other xbuffer */
451    main->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1);
452    main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2);
453    main->context_state = CTX_POSTPONED_ROW;
454  }
455}
456
457
458/*
459 * Process some data.
460 * Final pass of two-pass quantization: just call the postprocessor.
461 * Source data will be the postprocessor controller's internal buffer.
462 */
463
464#ifdef QUANT_2PASS_SUPPORTED
465
466METHODDEF(void)
467process_data_crank_post (j_decompress_ptr cinfo,
468                         JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
469                         JDIMENSION out_rows_avail)
470{
471  (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
472                                     (JDIMENSION *) NULL, (JDIMENSION) 0,
473                                     output_buf, out_row_ctr, out_rows_avail);
474}
475
476#endif /* QUANT_2PASS_SUPPORTED */
477
478
479/*
480 * Initialize main buffer controller.
481 */
482
483GLOBAL(void)
484jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
485{
486  my_main_ptr main;
487  int ci, rgroup, ngroups;
488  jpeg_component_info *compptr;
489
490  main = (my_main_ptr)
491    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
492                                SIZEOF(my_main_controller));
493  cinfo->main = (struct jpeg_d_main_controller *) main;
494  main->pub.start_pass = start_pass_main;
495
496  if (need_full_buffer)         /* shouldn't happen */
497    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
498
499  /* Allocate the workspace.
500   * ngroups is the number of row groups we need.
501   */
502  if (cinfo->upsample->need_context_rows) {
503    if (cinfo->min_DCT_scaled_size < 2) /* unsupported, see comments above */
504      ERREXIT(cinfo, JERR_NOTIMPL);
505    alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
506    ngroups = cinfo->min_DCT_scaled_size + 2;
507  } else {
508    ngroups = cinfo->min_DCT_scaled_size;
509  }
510
511  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
512       ci++, compptr++) {
513    rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
514      cinfo->min_DCT_scaled_size; /* height of a row group of component */
515    main->buffer[ci] = (*cinfo->mem->alloc_sarray)
516                        ((j_common_ptr) cinfo, JPOOL_IMAGE,
517                         compptr->width_in_blocks * compptr->DCT_scaled_size,
518                         (JDIMENSION) (rgroup * ngroups));
519  }
520}
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