1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jccoefct.c
7 *
8 * Copyright (C) 1994-1997, Thomas G. Lane.
9 * This file is part of the Independent JPEG Group's software.
10 * For conditions of distribution and use, see the accompanying README file.
11 *
12 * This file contains the coefficient buffer controller for compression.
13 * This controller is the top level of the JPEG compressor proper.
14 * The coefficient buffer lies between forward-DCT and entropy encoding steps.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20
21
22/* We use a full-image coefficient buffer when doing Huffman optimization,
23 * and also for writing multiple-scan JPEG files. In all cases, the DCT
24 * step is run during the first pass, and subsequent passes need only read
25 * the buffered coefficients.
26 */
27#ifdef ENTROPY_OPT_SUPPORTED
28#define FULL_COEF_BUFFER_SUPPORTED
29#else
30#ifdef C_MULTISCAN_FILES_SUPPORTED
31#define FULL_COEF_BUFFER_SUPPORTED
32#endif
33#endif
34
35
36/* Private buffer controller object */
37
38typedef struct {
39 struct jpeg_c_coef_controller pub; /* public fields */
40
41 JDIMENSION iMCU_row_num; /* iMCU row # within image */
42 JDIMENSION mcu_ctr; /* counts MCUs processed in current row */
43 int MCU_vert_offset; /* counts MCU rows within iMCU row */
44 int MCU_rows_per_iMCU_row; /* number of such rows needed */
45
46 /* For single-pass compression, it's sufficient to buffer just one MCU
47 * (although this may prove a bit slow in practice). We allocate a
48 * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
49 * MCU constructed and sent. (On 80x86, the workspace is FAR even though
50 * it's not really very big; this is to keep the module interfaces unchanged
51 * when a large coefficient buffer is necessary.)
52 * In multi-pass modes, this array points to the current MCU's blocks
53 * within the virtual arrays.
54 */
55 JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
56
57 /* In multi-pass modes, we need a virtual block array for each component. */
58 jvirt_barray_ptr whole_image[MAX_COMPONENTS];
59} my_coef_controller;
60
61typedef my_coef_controller * my_coef_ptr;
62
63
64/* Forward declarations */
65METHODDEF(boolean) compress_data
66 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
67#ifdef FULL_COEF_BUFFER_SUPPORTED
68METHODDEF(boolean) compress_first_pass
69 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
70METHODDEF(boolean) compress_output
71 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
72#endif
73
74
75LOCAL(void)
76start_iMCU_row (j_compress_ptr cinfo)
77/* Reset within-iMCU-row counters for a new row */
78{
79 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
80
81 /* In an interleaved scan, an MCU row is the same as an iMCU row.
82 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
83 * But at the bottom of the image, process only what's left.
84 */
85 if (cinfo->comps_in_scan > 1) {
86 coef->MCU_rows_per_iMCU_row = 1;
87 } else {
88 if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
89 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
90 else
91 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
92 }
93
94 coef->mcu_ctr = 0;
95 coef->MCU_vert_offset = 0;
96}
97
98
99/*
100 * Initialize for a processing pass.
101 */
102
103METHODDEF(void)
104start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
105{
106 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
107
108 coef->iMCU_row_num = 0;
109 start_iMCU_row(cinfo);
110
111 switch (pass_mode) {
112 case JBUF_PASS_THRU:
113 if (coef->whole_image[0] != NULL)
114 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
115 coef->pub.compress_data = compress_data;
116 break;
117#ifdef FULL_COEF_BUFFER_SUPPORTED
118 case JBUF_SAVE_AND_PASS:
119 if (coef->whole_image[0] == NULL)
120 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
121 coef->pub.compress_data = compress_first_pass;
122 break;
123 case JBUF_CRANK_DEST:
124 if (coef->whole_image[0] == NULL)
125 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
126 coef->pub.compress_data = compress_output;
127 break;
128#endif
129 default:
130 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
131 break;
132 }
133}
134
135
136/*
137 * Process some data in the single-pass case.
138 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
139 * per call, ie, v_samp_factor block rows for each component in the image.
140 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
141 *
142 * NB: input_buf contains a plane for each component in image,
143 * which we index according to the component's SOF position.
144 */
145
146METHODDEF(boolean)
147compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_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, bi, ci, yindex, yoffset, blockcnt;
154 JDIMENSION ypos, xpos;
155 jpeg_component_info *compptr;
156
157 /* Loop to write as much as one whole iMCU row */
158 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
159 yoffset++) {
160 for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
161 MCU_col_num++) {
162 /* Determine where data comes from in input_buf and do the DCT thing.
163 * Each call on forward_DCT processes a horizontal row of DCT blocks
164 * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
165 * sequentially. Dummy blocks at the right or bottom edge are filled in
166 * specially. The data in them does not matter for image reconstruction,
167 * so we fill them with values that will encode to the smallest amount of
168 * data, viz: all zeroes in the AC entries, DC entries equal to previous
169 * block's DC value. (Thanks to Thomas Kinsman for this idea.)
170 */
171 blkn = 0;
172 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
173 compptr = cinfo->cur_comp_info[ci];
174 blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
175 : compptr->last_col_width;
176 xpos = MCU_col_num * compptr->MCU_sample_width;
177 ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
178 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
179 if (coef->iMCU_row_num < last_iMCU_row ||
180 yoffset+yindex < compptr->last_row_height) {
181 (*cinfo->fdct->forward_DCT) (cinfo, compptr,
182 input_buf[compptr->component_index],
183 coef->MCU_buffer[blkn],
184 ypos, xpos, (JDIMENSION) blockcnt);
185 if (blockcnt < compptr->MCU_width) {
186 /* Create some dummy blocks at the right edge of the image. */
187 jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
188 (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
189 for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
190 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
191 }
192 }
193 } else {
194 /* Create a row of dummy blocks at the bottom of the image. */
195 jzero_far((void FAR *) coef->MCU_buffer[blkn],
196 compptr->MCU_width * SIZEOF(JBLOCK));
197 for (bi = 0; bi < compptr->MCU_width; bi++) {
198 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
199 }
200 }
201 blkn += compptr->MCU_width;
202 ypos += DCTSIZE;
203 }
204 }
205 /* Try to write the MCU. In event of a suspension failure, we will
206 * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
207 */
208 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
209 /* Suspension forced; update state counters and exit */
210 coef->MCU_vert_offset = yoffset;
211 coef->mcu_ctr = MCU_col_num;
212 return FALSE;
213 }
214 }
215 /* Completed an MCU row, but perhaps not an iMCU row */
216 coef->mcu_ctr = 0;
217 }
218 /* Completed the iMCU row, advance counters for next one */
219 coef->iMCU_row_num++;
220 start_iMCU_row(cinfo);
221 return TRUE;
222}
223
224
225#ifdef FULL_COEF_BUFFER_SUPPORTED
226
227/*
228 * Process some data in the first pass of a multi-pass case.
229 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
230 * per call, ie, v_samp_factor block rows for each component in the image.
231 * This amount of data is read from the source buffer, DCT'd and quantized,
232 * and saved into the virtual arrays. We also generate suitable dummy blocks
233 * as needed at the right and lower edges. (The dummy blocks are constructed
234 * in the virtual arrays, which have been padded appropriately.) This makes
235 * it possible for subsequent passes not to worry about real vs. dummy blocks.
236 *
237 * We must also emit the data to the entropy encoder. This is conveniently
238 * done by calling compress_output() after we've loaded the current strip
239 * of the virtual arrays.
240 *
241 * NB: input_buf contains a plane for each component in image. All
242 * components are DCT'd and loaded into the virtual arrays in this pass.
243 * However, it may be that only a subset of the components are emitted to
244 * the entropy encoder during this first pass; be careful about looking
245 * at the scan-dependent variables (MCU dimensions, etc).
246 */
247
248METHODDEF(boolean)
249compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
250{
251 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
252 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
253 JDIMENSION blocks_across, MCUs_across, MCUindex;
254 int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
255 JCOEF lastDC;
256 jpeg_component_info *compptr;
257 JBLOCKARRAY buffer;
258 JBLOCKROW thisblockrow, lastblockrow;
259
260 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
261 ci++, compptr++) {
262 /* Align the virtual buffer for this component. */
263 buffer = (*cinfo->mem->access_virt_barray)
264 ((j_common_ptr) cinfo, coef->whole_image[ci],
265 coef->iMCU_row_num * compptr->v_samp_factor,
266 (JDIMENSION) compptr->v_samp_factor, TRUE);
267 /* Count non-dummy DCT block rows in this iMCU row. */
268 if (coef->iMCU_row_num < last_iMCU_row)
269 block_rows = compptr->v_samp_factor;
270 else {
271 /* NB: can't use last_row_height here, since may not be set! */
272 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
273 if (block_rows == 0) block_rows = compptr->v_samp_factor;
274 }
275 blocks_across = compptr->width_in_blocks;
276 h_samp_factor = compptr->h_samp_factor;
277 /* Count number of dummy blocks to be added at the right margin. */
278 ndummy = (int) (blocks_across % h_samp_factor);
279 if (ndummy > 0)
280 ndummy = h_samp_factor - ndummy;
281 /* Perform DCT for all non-dummy blocks in this iMCU row. Each call
282 * on forward_DCT processes a complete horizontal row of DCT blocks.
283 */
284 for (block_row = 0; block_row < block_rows; block_row++) {
285 thisblockrow = buffer[block_row];
286 (*cinfo->fdct->forward_DCT) (cinfo, compptr,
287 input_buf[ci], thisblockrow,
288 (JDIMENSION) (block_row * DCTSIZE),
289 (JDIMENSION) 0, blocks_across);
290 if (ndummy > 0) {
291 /* Create dummy blocks at the right edge of the image. */
292 thisblockrow += blocks_across; /* => first dummy block */
293 jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
294 lastDC = thisblockrow[-1][0];
295 for (bi = 0; bi < ndummy; bi++) {
296 thisblockrow[bi][0] = lastDC;
297 }
298 }
299 }
300 /* If at end of image, create dummy block rows as needed.
301 * The tricky part here is that within each MCU, we want the DC values
302 * of the dummy blocks to match the last real block's DC value.
303 * This squeezes a few more bytes out of the resulting file...
304 */
305 if (coef->iMCU_row_num == last_iMCU_row) {
306 blocks_across += ndummy; /* include lower right corner */
307 MCUs_across = blocks_across / h_samp_factor;
308 for (block_row = block_rows; block_row < compptr->v_samp_factor;
309 block_row++) {
310 thisblockrow = buffer[block_row];
311 lastblockrow = buffer[block_row-1];
312 jzero_far((void FAR *) thisblockrow,
313 (size_t) (blocks_across * SIZEOF(JBLOCK)));
314 for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
315 lastDC = lastblockrow[h_samp_factor-1][0];
316 for (bi = 0; bi < h_samp_factor; bi++) {
317 thisblockrow[bi][0] = lastDC;
318 }
319 thisblockrow += h_samp_factor; /* advance to next MCU in row */
320 lastblockrow += h_samp_factor;
321 }
322 }
323 }
324 }
325 /* NB: compress_output will increment iMCU_row_num if successful.
326 * A suspension return will result in redoing all the work above next time.
327 */
328
329 /* Emit data to the entropy encoder, sharing code with subsequent passes */
330 return compress_output(cinfo, input_buf);
331}
332
333
334/*
335 * Process some data in subsequent passes of a multi-pass case.
336 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
337 * per call, ie, v_samp_factor block rows for each component in the scan.
338 * The data is obtained from the virtual arrays and fed to the entropy coder.
339 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
340 *
341 * NB: input_buf is ignored; it is likely to be a NULL pointer.
342 */
343
344METHODDEF(boolean)
345compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
346{
347 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
348 JDIMENSION MCU_col_num; /* index of current MCU within row */
349 int blkn, ci, xindex, yindex, yoffset;
350 JDIMENSION start_col;
351 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
352 JBLOCKROW buffer_ptr;
353 jpeg_component_info *compptr;
354
355 /* Align the virtual buffers for the components used in this scan.
356 * NB: during first pass, this is safe only because the buffers will
357 * already be aligned properly, so jmemmgr.c won't need to do any I/O.
358 */
359 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
360 compptr = cinfo->cur_comp_info[ci];
361 buffer[ci] = (*cinfo->mem->access_virt_barray)
362 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
363 coef->iMCU_row_num * compptr->v_samp_factor,
364 (JDIMENSION) compptr->v_samp_factor, FALSE);
365 }
366
367 /* Loop to process one whole iMCU row */
368 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
369 yoffset++) {
370 for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
371 MCU_col_num++) {
372 /* Construct list of pointers to DCT blocks belonging to this MCU */
373 blkn = 0; /* index of current DCT block within MCU */
374 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
375 compptr = cinfo->cur_comp_info[ci];
376 start_col = MCU_col_num * compptr->MCU_width;
377 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
378 buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
379 for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
380 coef->MCU_buffer[blkn++] = buffer_ptr++;
381 }
382 }
383 }
384 /* Try to write the MCU. */
385 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
386 /* Suspension forced; update state counters and exit */
387 coef->MCU_vert_offset = yoffset;
388 coef->mcu_ctr = MCU_col_num;
389 return FALSE;
390 }
391 }
392 /* Completed an MCU row, but perhaps not an iMCU row */
393 coef->mcu_ctr = 0;
394 }
395 /* Completed the iMCU row, advance counters for next one */
396 coef->iMCU_row_num++;
397 start_iMCU_row(cinfo);
398 return TRUE;
399}
400
401#endif /* FULL_COEF_BUFFER_SUPPORTED */
402
403
404/*
405 * Initialize coefficient buffer controller.
406 */
407
408GLOBAL(void)
409jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
410{
411 my_coef_ptr coef;
412
413 coef = (my_coef_ptr)
414 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
415 SIZEOF(my_coef_controller));
416 cinfo->coef = (struct jpeg_c_coef_controller *) coef;
417 coef->pub.start_pass = start_pass_coef;
418
419 /* Create the coefficient buffer. */
420 if (need_full_buffer) {
421#ifdef FULL_COEF_BUFFER_SUPPORTED
422 /* Allocate a full-image virtual array for each component, */
423 /* padded to a multiple of samp_factor DCT blocks in each direction. */
424 int ci;
425 jpeg_component_info *compptr;
426
427 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
428 ci++, compptr++) {
429 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
430 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
431 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
432 (long) compptr->h_samp_factor),
433 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
434 (long) compptr->v_samp_factor),
435 (JDIMENSION) compptr->v_samp_factor);
436 }
437#else
438 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
439#endif
440 } else {
441 /* We only need a single-MCU buffer. */
442 JBLOCKROW buffer;
443 int i;
444
445 buffer = (JBLOCKROW)
446 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
447 C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
448 for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
449 coef->MCU_buffer[i] = buffer + i;
450 }
451 coef->whole_image[0] = NULL; /* flag for no virtual arrays */
452 }
453}
454