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 coefficient buffer controller for compression.
9
* This controller is the top level of the JPEG compressor proper.
10
* The coefficient buffer lies between forward-DCT and entropy encoding steps.
13
#define JPEG_INTERNALS
18
/* We use a full-image coefficient buffer when doing Huffman optimization,
19
* and also for writing multiple-scan JPEG files. In all cases, the DCT
20
* step is run during the first pass, and subsequent passes need only read
21
* the buffered coefficients.
23
#ifdef ENTROPY_OPT_SUPPORTED
24
#define FULL_COEF_BUFFER_SUPPORTED
26
#ifdef C_MULTISCAN_FILES_SUPPORTED
27
#define FULL_COEF_BUFFER_SUPPORTED
32
/* Private buffer controller object */
35
struct jpeg_c_coef_controller pub; /* public fields */
37
JDIMENSION iMCU_row_num; /* iMCU row # within image */
38
JDIMENSION mcu_ctr; /* counts MCUs processed in current row */
39
int MCU_vert_offset; /* counts MCU rows within iMCU row */
40
int MCU_rows_per_iMCU_row; /* number of such rows needed */
42
/* For single-pass compression, it's sufficient to buffer just one MCU
43
* (although this may prove a bit slow in practice). We allocate a
44
* workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
45
* MCU constructed and sent. (On 80x86, the workspace is FAR even though
46
* it's not really very big; this is to keep the module interfaces unchanged
47
* when a large coefficient buffer is necessary.)
48
* In multi-pass modes, this array points to the current MCU's blocks
49
* within the virtual arrays.
51
JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
53
/* In multi-pass modes, we need a virtual block array for each component. */
54
jvirt_barray_ptr whole_image[MAX_COMPONENTS];
57
typedef my_coef_controller * my_coef_ptr;
60
/* Forward declarations */
61
METHODDEF boolean compress_data
62
JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
63
#ifdef FULL_COEF_BUFFER_SUPPORTED
64
METHODDEF boolean compress_first_pass
65
JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
66
METHODDEF boolean compress_output
67
JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
72
start_iMCU_row (j_compress_ptr cinfo)
73
/* Reset within-iMCU-row counters for a new row */
75
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
77
/* In an interleaved scan, an MCU row is the same as an iMCU row.
78
* In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
79
* But at the bottom of the image, process only what's left.
81
if (cinfo->comps_in_scan > 1) {
82
coef->MCU_rows_per_iMCU_row = 1;
84
if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
85
coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
87
coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
91
coef->MCU_vert_offset = 0;
96
* Initialize for a processing pass.
100
start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
102
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
104
coef->iMCU_row_num = 0;
105
start_iMCU_row(cinfo);
109
if (coef->whole_image[0] != NULL)
110
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
111
coef->pub.compress_data = compress_data;
113
#ifdef FULL_COEF_BUFFER_SUPPORTED
114
case JBUF_SAVE_AND_PASS:
115
if (coef->whole_image[0] == NULL)
116
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
117
coef->pub.compress_data = compress_first_pass;
119
case JBUF_CRANK_DEST:
120
if (coef->whole_image[0] == NULL)
121
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
122
coef->pub.compress_data = compress_output;
126
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
133
* Process some data in the single-pass case.
134
* We process the equivalent of one fully interleaved MCU row ("iMCU" row)
135
* per call, ie, v_samp_factor block rows for each component in the image.
136
* Returns TRUE if the iMCU row is completed, FALSE if suspended.
138
* NB: input_buf contains a plane for each component in image.
139
* For single pass, this is the same as the components in the scan.
143
compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
145
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
146
JDIMENSION MCU_col_num; /* index of current MCU within row */
147
JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
148
JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
149
int blkn, bi, ci, yindex, yoffset, blockcnt;
150
JDIMENSION ypos, xpos;
151
jpeg_component_info *compptr;
153
/* Loop to write as much as one whole iMCU row */
154
for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
156
for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
158
/* Determine where data comes from in input_buf and do the DCT thing.
159
* Each call on forward_DCT processes a horizontal row of DCT blocks
160
* as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
161
* sequentially. Dummy blocks at the right or bottom edge are filled in
162
* specially. The data in them does not matter for image reconstruction,
163
* so we fill them with values that will encode to the smallest amount of
164
* data, viz: all zeroes in the AC entries, DC entries equal to previous
165
* block's DC value. (Thanks to Thomas Kinsman for this idea.)
168
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
169
compptr = cinfo->cur_comp_info[ci];
170
blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
171
: compptr->last_col_width;
172
xpos = MCU_col_num * compptr->MCU_sample_width;
173
ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
174
for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
175
if (coef->iMCU_row_num < last_iMCU_row ||
176
yoffset+yindex < compptr->last_row_height) {
177
(*cinfo->fdct->forward_DCT) (cinfo, compptr,
178
input_buf[ci], coef->MCU_buffer[blkn],
179
ypos, xpos, (JDIMENSION) blockcnt);
180
if (blockcnt < compptr->MCU_width) {
181
/* Create some dummy blocks at the right edge of the image. */
182
jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
183
(compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
184
for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
185
coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
189
/* Create a row of dummy blocks at the bottom of the image. */
190
jzero_far((void FAR *) coef->MCU_buffer[blkn],
191
compptr->MCU_width * SIZEOF(JBLOCK));
192
for (bi = 0; bi < compptr->MCU_width; bi++) {
193
coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
196
blkn += compptr->MCU_width;
200
/* Try to write the MCU. In event of a suspension failure, we will
201
* re-DCT the MCU on restart (a bit inefficient, could be fixed...)
203
if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
204
/* Suspension forced; update state counters and exit */
205
coef->MCU_vert_offset = yoffset;
206
coef->mcu_ctr = MCU_col_num;
210
/* Completed an MCU row, but perhaps not an iMCU row */
213
/* Completed the iMCU row, advance counters for next one */
214
coef->iMCU_row_num++;
215
start_iMCU_row(cinfo);
220
#ifdef FULL_COEF_BUFFER_SUPPORTED
223
* Process some data in the first pass of a multi-pass case.
224
* We process the equivalent of one fully interleaved MCU row ("iMCU" row)
225
* per call, ie, v_samp_factor block rows for each component in the image.
226
* This amount of data is read from the source buffer, DCT'd and quantized,
227
* and saved into the virtual arrays. We also generate suitable dummy blocks
228
* as needed at the right and lower edges. (The dummy blocks are constructed
229
* in the virtual arrays, which have been padded appropriately.) This makes
230
* it possible for subsequent passes not to worry about real vs. dummy blocks.
232
* We must also emit the data to the entropy encoder. This is conveniently
233
* done by calling compress_output() after we've loaded the current strip
234
* of the virtual arrays.
236
* NB: input_buf contains a plane for each component in image. All
237
* components are DCT'd and loaded into the virtual arrays in this pass.
238
* However, it may be that only a subset of the components are emitted to
239
* the entropy encoder during this first pass; be careful about looking
240
* at the scan-dependent variables (MCU dimensions, etc).
244
compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
246
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
247
JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
248
JDIMENSION blocks_across, MCUs_across, MCUindex;
249
int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
251
jpeg_component_info *compptr;
253
JBLOCKROW thisblockrow, lastblockrow;
255
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
257
/* Align the virtual buffer for this component. */
258
buffer = (*cinfo->mem->access_virt_barray)
259
((j_common_ptr) cinfo, coef->whole_image[ci],
260
coef->iMCU_row_num * compptr->v_samp_factor,
261
(JDIMENSION) compptr->v_samp_factor, TRUE);
262
/* Count non-dummy DCT block rows in this iMCU row. */
263
if (coef->iMCU_row_num < last_iMCU_row)
264
block_rows = compptr->v_samp_factor;
266
/* NB: can't use last_row_height here, since may not be set! */
267
block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
268
if (block_rows == 0) block_rows = compptr->v_samp_factor;
270
blocks_across = compptr->width_in_blocks;
271
h_samp_factor = compptr->h_samp_factor;
272
/* Count number of dummy blocks to be added at the right margin. */
273
ndummy = (int) (blocks_across % h_samp_factor);
275
ndummy = h_samp_factor - ndummy;
276
/* Perform DCT for all non-dummy blocks in this iMCU row. Each call
277
* on forward_DCT processes a complete horizontal row of DCT blocks.
279
for (block_row = 0; block_row < block_rows; block_row++) {
280
thisblockrow = buffer[block_row];
281
(*cinfo->fdct->forward_DCT) (cinfo, compptr,
282
input_buf[ci], thisblockrow,
283
(JDIMENSION) (block_row * DCTSIZE),
284
(JDIMENSION) 0, blocks_across);
286
/* Create dummy blocks at the right edge of the image. */
287
thisblockrow += blocks_across; /* => first dummy block */
288
jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
289
lastDC = thisblockrow[-1][0];
290
for (bi = 0; bi < ndummy; bi++) {
291
thisblockrow[bi][0] = lastDC;
295
/* If at end of image, create dummy block rows as needed.
296
* The tricky part here is that within each MCU, we want the DC values
297
* of the dummy blocks to match the last real block's DC value.
298
* This squeezes a few more bytes out of the resulting file...
300
if (coef->iMCU_row_num == last_iMCU_row) {
301
blocks_across += ndummy; /* include lower right corner */
302
MCUs_across = blocks_across / h_samp_factor;
303
for (block_row = block_rows; block_row < compptr->v_samp_factor;
305
thisblockrow = buffer[block_row];
306
lastblockrow = buffer[block_row-1];
307
jzero_far((void FAR *) thisblockrow,
308
(size_t) (blocks_across * SIZEOF(JBLOCK)));
309
for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
310
lastDC = lastblockrow[h_samp_factor-1][0];
311
for (bi = 0; bi < h_samp_factor; bi++) {
312
thisblockrow[bi][0] = lastDC;
314
thisblockrow += h_samp_factor; /* advance to next MCU in row */
315
lastblockrow += h_samp_factor;
320
/* NB: compress_output will increment iMCU_row_num if successful.
321
* A suspension return will result in redoing all the work above next time.
324
/* Emit data to the entropy encoder, sharing code with subsequent passes */
325
return compress_output(cinfo, input_buf);
330
* Process some data in subsequent passes of a multi-pass case.
331
* We process the equivalent of one fully interleaved MCU row ("iMCU" row)
332
* per call, ie, v_samp_factor block rows for each component in the scan.
333
* The data is obtained from the virtual arrays and fed to the entropy coder.
334
* Returns TRUE if the iMCU row is completed, FALSE if suspended.
336
* NB: input_buf is ignored; it is likely to be a NULL pointer.
340
compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
342
my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
343
JDIMENSION MCU_col_num; /* index of current MCU within row */
344
int blkn, ci, xindex, yindex, yoffset;
345
JDIMENSION start_col;
346
JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
347
JBLOCKROW buffer_ptr;
348
jpeg_component_info *compptr;
350
/* Align the virtual buffers for the components used in this scan.
351
* NB: during first pass, this is safe only because the buffers will
352
* already be aligned properly, so jmemmgr.c won't need to do any I/O.
354
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
355
compptr = cinfo->cur_comp_info[ci];
356
buffer[ci] = (*cinfo->mem->access_virt_barray)
357
((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
358
coef->iMCU_row_num * compptr->v_samp_factor,
359
(JDIMENSION) compptr->v_samp_factor, FALSE);
362
/* Loop to process one whole iMCU row */
363
for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
365
for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
367
/* Construct list of pointers to DCT blocks belonging to this MCU */
368
blkn = 0; /* index of current DCT block within MCU */
369
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
370
compptr = cinfo->cur_comp_info[ci];
371
start_col = MCU_col_num * compptr->MCU_width;
372
for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
373
buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
374
for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
375
coef->MCU_buffer[blkn++] = buffer_ptr++;
379
/* Try to write the MCU. */
380
if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
381
/* Suspension forced; update state counters and exit */
382
coef->MCU_vert_offset = yoffset;
383
coef->mcu_ctr = MCU_col_num;
387
/* Completed an MCU row, but perhaps not an iMCU row */
390
/* Completed the iMCU row, advance counters for next one */
391
coef->iMCU_row_num++;
392
start_iMCU_row(cinfo);
396
#endif /* FULL_COEF_BUFFER_SUPPORTED */
400
* Initialize coefficient buffer controller.
404
jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
409
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
410
SIZEOF(my_coef_controller));
411
cinfo->coef = (struct jpeg_c_coef_controller *) coef;
412
coef->pub.start_pass = start_pass_coef;
414
/* Create the coefficient buffer. */
415
if (need_full_buffer) {
416
#ifdef FULL_COEF_BUFFER_SUPPORTED
417
/* Allocate a full-image virtual array for each component, */
418
/* padded to a multiple of samp_factor DCT blocks in each direction. */
420
jpeg_component_info *compptr;
422
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
424
coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
425
((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
426
(JDIMENSION) jround_up((long) compptr->width_in_blocks,
427
(long) compptr->h_samp_factor),
428
(JDIMENSION) jround_up((long) compptr->height_in_blocks,
429
(long) compptr->v_samp_factor),
430
(JDIMENSION) compptr->v_samp_factor);
433
ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
436
/* We only need a single-MCU buffer. */
441
(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
442
C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
443
for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
444
coef->MCU_buffer[i] = buffer + i;
446
coef->whole_image[0] = NULL; /* flag for no virtual arrays */
added
removed
code/jpeg-6/jccoefct.c
