4
* Copyright (C) 1994-1995, 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.
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.
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.
16
#define JPEG_INTERNALS
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.
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
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.
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.
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.
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.)
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:
82
* master pointer --> 0 master pointer --> 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
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).
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.
112
/* Private buffer controller object */
115
struct jpeg_d_main_controller pub; /* public fields */
117
/* Pointer to allocated workspace (M or M+2 row groups). */
118
JSAMPARRAY buffer[MAX_COMPONENTS];
120
boolean buffer_full; /* Have we gotten an iMCU row from decoder? */
121
JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */
123
/* Remaining fields are only used in the context case. */
125
/* These are the master pointers to the funny-order pointer lists. */
126
JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */
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;
134
typedef my_main_controller * my_main_ptr;
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 */
142
/* Forward declarations */
143
METHODDEF void process_data_simple_main
144
JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
145
JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
146
METHODDEF 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
150
METHODDEF void process_data_crank_post
151
JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
152
JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
157
alloc_funny_pointers (j_decompress_ptr cinfo)
158
/* Allocate space for the funny pointer lists.
159
* This is done only once, not once per pass.
162
// bk001204 - no use main
163
my_main_ptr jmain = (my_main_ptr) cinfo->main;
165
int M = cinfo->min_DCT_scaled_size;
166
jpeg_component_info *compptr;
169
/* Get top-level space for component array pointers.
170
* We alloc both arrays with one call to save a few cycles.
172
jmain->xbuffer[0] = (JSAMPIMAGE)
173
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
174
cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
175
jmain->xbuffer[1] = jmain->xbuffer[0] + cinfo->num_components;
177
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
179
rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
180
cinfo->min_DCT_scaled_size; /* height of a row group of component */
181
/* Get space for pointer lists --- M+4 row groups in each list.
182
* We alloc both pointer lists with one call to save a few cycles.
185
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
186
2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
187
xbuf += rgroup; /* want one row group at negative offsets */
188
jmain->xbuffer[0][ci] = xbuf;
189
xbuf += rgroup * (M + 4);
190
jmain->xbuffer[1][ci] = xbuf;
196
make_funny_pointers (j_decompress_ptr cinfo)
197
/* Create the funny pointer lists discussed in the comments above.
198
* The actual workspace is already allocated (in main->buffer),
199
* and the space for the pointer lists is allocated too.
200
* This routine just fills in the curiously ordered lists.
201
* This will be repeated at the beginning of each pass.
204
// bk001204 - no use main
205
my_main_ptr jmain = (my_main_ptr) cinfo->main;
207
int M = cinfo->min_DCT_scaled_size;
208
jpeg_component_info *compptr;
209
JSAMPARRAY buf, xbuf0, xbuf1;
211
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
213
rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
214
cinfo->min_DCT_scaled_size; /* height of a row group of component */
215
xbuf0 = jmain->xbuffer[0][ci];
216
xbuf1 = jmain->xbuffer[1][ci];
217
/* First copy the workspace pointers as-is */
218
buf = jmain->buffer[ci];
219
for (i = 0; i < rgroup * (M + 2); i++) {
220
xbuf0[i] = xbuf1[i] = buf[i];
222
/* In the second list, put the last four row groups in swapped order */
223
for (i = 0; i < rgroup * 2; i++) {
224
xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
225
xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
227
/* The wraparound pointers at top and bottom will be filled later
228
* (see set_wraparound_pointers, below). Initially we want the "above"
229
* pointers to duplicate the first actual data line. This only needs
230
* to happen in xbuffer[0].
232
for (i = 0; i < rgroup; i++) {
233
xbuf0[i - rgroup] = xbuf0[0];
240
set_wraparound_pointers (j_decompress_ptr cinfo)
241
/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
242
* This changes the pointer list state from top-of-image to the normal state.
245
// bk001204 - no use main
246
my_main_ptr jmain = (my_main_ptr) cinfo->main;
248
int M = cinfo->min_DCT_scaled_size;
249
jpeg_component_info *compptr;
250
JSAMPARRAY xbuf0, xbuf1;
252
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
254
rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
255
cinfo->min_DCT_scaled_size; /* height of a row group of component */
256
xbuf0 = jmain->xbuffer[0][ci];
257
xbuf1 = jmain->xbuffer[1][ci];
258
for (i = 0; i < rgroup; i++) {
259
xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
260
xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
261
xbuf0[rgroup*(M+2) + i] = xbuf0[i];
262
xbuf1[rgroup*(M+2) + i] = xbuf1[i];
269
set_bottom_pointers (j_decompress_ptr cinfo)
270
/* Change the pointer lists to duplicate the last sample row at the bottom
271
* of the image. whichptr indicates which xbuffer holds the final iMCU row.
272
* Also sets rowgroups_avail to indicate number of nondummy row groups in row.
275
// bk001204 - no use main
276
my_main_ptr jmain = (my_main_ptr) cinfo->main;
277
int ci, i, rgroup, iMCUheight, rows_left;
278
jpeg_component_info *compptr;
281
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
283
/* Count sample rows in one iMCU row and in one row group */
284
iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
285
rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
286
/* Count nondummy sample rows remaining for this component */
287
rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
288
if (rows_left == 0) rows_left = iMCUheight;
289
/* Count nondummy row groups. Should get same answer for each component,
290
* so we need only do it once.
293
jmain->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
295
/* Duplicate the last real sample row rgroup*2 times; this pads out the
296
* last partial rowgroup and ensures at least one full rowgroup of context.
298
xbuf = jmain->xbuffer[jmain->whichptr][ci];
299
for (i = 0; i < rgroup * 2; i++) {
300
xbuf[rows_left + i] = xbuf[rows_left-1];
307
* Initialize for a processing pass.
311
start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
313
// bk001204 - no use main
314
my_main_ptr jmain = (my_main_ptr) cinfo->main;
318
if (cinfo->upsample->need_context_rows) {
319
jmain->pub.process_data = process_data_context_main;
320
make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
321
jmain->whichptr = 0; /* Read first iMCU row into xbuffer[0] */
322
jmain->context_state = CTX_PREPARE_FOR_IMCU;
323
jmain->iMCU_row_ctr = 0;
325
/* Simple case with no context needed */
326
jmain->pub.process_data = process_data_simple_main;
328
jmain->buffer_full = FALSE; /* Mark buffer empty */
329
jmain->rowgroup_ctr = 0;
331
#ifdef QUANT_2PASS_SUPPORTED
332
case JBUF_CRANK_DEST:
333
/* For last pass of 2-pass quantization, just crank the postprocessor */
334
jmain->pub.process_data = process_data_crank_post;
338
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
346
* This handles the simple case where no context is required.
350
process_data_simple_main (j_decompress_ptr cinfo,
351
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
352
JDIMENSION out_rows_avail)
354
// bk001204 - no use main
355
my_main_ptr jmain = (my_main_ptr) cinfo->main;
356
JDIMENSION rowgroups_avail;
358
/* Read input data if we haven't filled the main buffer yet */
359
if (! jmain->buffer_full) {
360
if (! (*cinfo->coef->decompress_data) (cinfo, jmain->buffer))
361
return; /* suspension forced, can do nothing more */
362
jmain->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
365
/* There are always min_DCT_scaled_size row groups in an iMCU row. */
366
rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size;
367
/* Note: at the bottom of the image, we may pass extra garbage row groups
368
* to the postprocessor. The postprocessor has to check for bottom
369
* of image anyway (at row resolution), so no point in us doing it too.
372
/* Feed the postprocessor */
373
(*cinfo->post->post_process_data) (cinfo, jmain->buffer,
374
&jmain->rowgroup_ctr, rowgroups_avail,
375
output_buf, out_row_ctr, out_rows_avail);
377
/* Has postprocessor consumed all the data yet? If so, mark buffer empty */
378
if (jmain->rowgroup_ctr >= rowgroups_avail) {
379
jmain->buffer_full = FALSE;
380
jmain->rowgroup_ctr = 0;
387
* This handles the case where context rows must be provided.
391
process_data_context_main (j_decompress_ptr cinfo,
392
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
393
JDIMENSION out_rows_avail)
395
// bk001204 - no use main
396
my_main_ptr jmain = (my_main_ptr) cinfo->main;
398
/* Read input data if we haven't filled the main buffer yet */
399
if (! jmain->buffer_full) {
400
if (! (*cinfo->coef->decompress_data) (cinfo,
401
jmain->xbuffer[jmain->whichptr]))
402
return; /* suspension forced, can do nothing more */
403
jmain->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
404
jmain->iMCU_row_ctr++; /* count rows received */
407
/* Postprocessor typically will not swallow all the input data it is handed
408
* in one call (due to filling the output buffer first). Must be prepared
409
* to exit and restart. This switch lets us keep track of how far we got.
410
* Note that each case falls through to the next on successful completion.
412
switch (jmain->context_state) {
413
case CTX_POSTPONED_ROW:
414
/* Call postprocessor using previously set pointers for postponed row */
415
(*cinfo->post->post_process_data) (cinfo, jmain->xbuffer[jmain->whichptr],
416
&jmain->rowgroup_ctr, jmain->rowgroups_avail,
417
output_buf, out_row_ctr, out_rows_avail);
418
if (jmain->rowgroup_ctr < jmain->rowgroups_avail)
419
return; /* Need to suspend */
420
jmain->context_state = CTX_PREPARE_FOR_IMCU;
421
if (*out_row_ctr >= out_rows_avail)
422
return; /* Postprocessor exactly filled output buf */
424
case CTX_PREPARE_FOR_IMCU:
425
/* Prepare to process first M-1 row groups of this iMCU row */
426
jmain->rowgroup_ctr = 0;
427
jmain->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1);
428
/* Check for bottom of image: if so, tweak pointers to "duplicate"
429
* the last sample row, and adjust rowgroups_avail to ignore padding rows.
431
if (jmain->iMCU_row_ctr == cinfo->total_iMCU_rows)
432
set_bottom_pointers(cinfo);
433
jmain->context_state = CTX_PROCESS_IMCU;
435
case CTX_PROCESS_IMCU:
436
/* Call postprocessor using previously set pointers */
437
(*cinfo->post->post_process_data) (cinfo, jmain->xbuffer[jmain->whichptr],
438
&jmain->rowgroup_ctr, jmain->rowgroups_avail,
439
output_buf, out_row_ctr, out_rows_avail);
440
if (jmain->rowgroup_ctr < jmain->rowgroups_avail)
441
return; /* Need to suspend */
442
/* After the first iMCU, change wraparound pointers to normal state */
443
if (jmain->iMCU_row_ctr == 1)
444
set_wraparound_pointers(cinfo);
445
/* Prepare to load new iMCU row using other xbuffer list */
446
jmain->whichptr ^= 1; /* 0=>1 or 1=>0 */
447
jmain->buffer_full = FALSE;
448
/* Still need to process last row group of this iMCU row, */
449
/* which is saved at index M+1 of the other xbuffer */
450
jmain->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1);
451
jmain->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2);
452
jmain->context_state = CTX_POSTPONED_ROW;
459
* Final pass of two-pass quantization: just call the postprocessor.
460
* Source data will be the postprocessor controller's internal buffer.
463
#ifdef QUANT_2PASS_SUPPORTED
466
process_data_crank_post (j_decompress_ptr cinfo,
467
JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
468
JDIMENSION out_rows_avail)
470
(*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
471
(JDIMENSION *) NULL, (JDIMENSION) 0,
472
output_buf, out_row_ctr, out_rows_avail);
475
#endif /* QUANT_2PASS_SUPPORTED */
479
* Initialize main buffer controller.
483
jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
485
// bk001204 - no use main
487
int ci, rgroup, ngroups;
488
jpeg_component_info *compptr;
490
jmain = (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 *) jmain;
494
jmain->pub.start_pass = start_pass_main;
496
if (need_full_buffer) /* shouldn't happen */
497
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
499
/* Allocate the workspace.
500
* ngroups is the number of row groups we need.
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;
508
ngroups = cinfo->min_DCT_scaled_size;
511
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
513
rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
514
cinfo->min_DCT_scaled_size; /* height of a row group of component */
515
jmain->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));
added
removed
code/jpeg-6/jdmainct.c
