1/*
2 * jccoefct.c
3 *
4 * Copyright (C) 1994-1997, 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 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.
11 */
12
13#define JPEG_INTERNALS
14#include "jinclude.h"
15#include "jpeglib.h"
16
17
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.
22 */
23#ifdef ENTROPY_OPT_SUPPORTED
24#define FULL_COEF_BUFFER_SUPPORTED
25#else
26#ifdef C_MULTISCAN_FILES_SUPPORTED
27#define FULL_COEF_BUFFER_SUPPORTED
28#endif
29#endif
30
31
32/* Private buffer controller object */
33
34typedef struct {
35 struct jpeg_c_coef_controller pub; /* public fields */
36
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 */
41
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.
50 */
51 JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
52
53 /* In multi-pass modes, we need a virtual block array for each component. */
54 jvirt_barray_ptr whole_image[MAX_COMPONENTS];
55} my_coef_controller;
56
57typedef my_coef_controller * my_coef_ptr;
58
59
60/* Forward declarations */
61METHODDEF(boolean) compress_data
62 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
63#ifdef FULL_COEF_BUFFER_SUPPORTED
64METHODDEF(boolean) compress_first_pass
65 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
66METHODDEF(boolean) compress_output
67 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
68#endif
69
70
71LOCAL(void)
72start_iMCU_row (j_compress_ptr cinfo)
73/* Reset within-iMCU-row counters for a new row */
74{
75 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
76
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.
80 */
81 if (cinfo->comps_in_scan > 1) {
82 coef->MCU_rows_per_iMCU_row = 1;
83 } else {
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;
86 else
87 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
88 }
89
90 coef->mcu_ctr = 0;
91 coef->MCU_vert_offset = 0;
92}
93
94
95/*
96 * Initialize for a processing pass.
97 */
98
99METHODDEF(void)
100start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
101{
102 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
103
104 coef->iMCU_row_num = 0;
105 start_iMCU_row(cinfo);
106
107 switch (pass_mode) {
108 case JBUF_PASS_THRU:
109 if (coef->whole_image[0] != NULL)
110 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
111 coef->pub.compress_data = compress_data;
112 break;
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;
118 break;
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;
123 break;
124#endif
125 default:
126 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
127 break;
128 }
129}
130
131
132/*
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.
137 *
138 * NB: input_buf contains a plane for each component in image,
139 * which we index according to the component's SOF position.
140 */
141
142METHODDEF(boolean)
143compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
144{
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;
152
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;
155 yoffset++) {
156 for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
157 MCU_col_num++) {
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.)
166 */
167 blkn = 0;
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[compptr->component_index],
179 coef->MCU_buffer[blkn],
180 ypos, xpos, (JDIMENSION) blockcnt);
181 if (blockcnt < compptr->MCU_width) {
182 /* Create some dummy blocks at the right edge of the image. */
183 jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
184 (compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
185 for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
186 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
187 }
188 }
189 } else {
190 /* Create a row of dummy blocks at the bottom of the image. */
191 jzero_far((void FAR *) coef->MCU_buffer[blkn],
192 compptr->MCU_width * SIZEOF(JBLOCK));
193 for (bi = 0; bi < compptr->MCU_width; bi++) {
194 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
195 }
196 }
197 blkn += compptr->MCU_width;
198 ypos += DCTSIZE;
199 }
200 }
201 /* Try to write the MCU. In event of a suspension failure, we will
202 * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
203 */
204 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
205 /* Suspension forced; update state counters and exit */
206 coef->MCU_vert_offset = yoffset;
207 coef->mcu_ctr = MCU_col_num;
208 return FALSE;
209 }
210 }
211 /* Completed an MCU row, but perhaps not an iMCU row */
212 coef->mcu_ctr = 0;
213 }
214 /* Completed the iMCU row, advance counters for next one */
215 coef->iMCU_row_num++;
216 start_iMCU_row(cinfo);
217 return TRUE;
218}
219
220
221#ifdef FULL_COEF_BUFFER_SUPPORTED
222
223/*
224 * Process some data in the first pass of a multi-pass case.
225 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
226 * per call, ie, v_samp_factor block rows for each component in the image.
227 * This amount of data is read from the source buffer, DCT'd and quantized,
228 * and saved into the virtual arrays. We also generate suitable dummy blocks
229 * as needed at the right and lower edges. (The dummy blocks are constructed
230 * in the virtual arrays, which have been padded appropriately.) This makes
231 * it possible for subsequent passes not to worry about real vs. dummy blocks.
232 *
233 * We must also emit the data to the entropy encoder. This is conveniently
234 * done by calling compress_output() after we've loaded the current strip
235 * of the virtual arrays.
236 *
237 * NB: input_buf contains a plane for each component in image. All
238 * components are DCT'd and loaded into the virtual arrays in this pass.
239 * However, it may be that only a subset of the components are emitted to
240 * the entropy encoder during this first pass; be careful about looking
241 * at the scan-dependent variables (MCU dimensions, etc).
242 */
243
244METHODDEF(boolean)
245compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
246{
247 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
248 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
249 JDIMENSION blocks_across, MCUs_across, MCUindex;
250 int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
251 JCOEF lastDC;
252 jpeg_component_info *compptr;
253 JBLOCKARRAY buffer;
254 JBLOCKROW thisblockrow, lastblockrow;
255
256 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
257 ci++, compptr++) {
258 /* Align the virtual buffer for this component. */
259 buffer = (*cinfo->mem->access_virt_barray)
260 ((j_common_ptr) cinfo, coef->whole_image[ci],
261 coef->iMCU_row_num * compptr->v_samp_factor,
262 (JDIMENSION) compptr->v_samp_factor, TRUE);
263 /* Count non-dummy DCT block rows in this iMCU row. */
264 if (coef->iMCU_row_num < last_iMCU_row)
265 block_rows = compptr->v_samp_factor;
266 else {
267 /* NB: can't use last_row_height here, since may not be set! */
268 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
269 if (block_rows == 0) block_rows = compptr->v_samp_factor;
270 }
271 blocks_across = compptr->width_in_blocks;
272 h_samp_factor = compptr->h_samp_factor;
273 /* Count number of dummy blocks to be added at the right margin. */
274 ndummy = (int) (blocks_across % h_samp_factor);
275 if (ndummy > 0)
276 ndummy = h_samp_factor - ndummy;
277 /* Perform DCT for all non-dummy blocks in this iMCU row. Each call
278 * on forward_DCT processes a complete horizontal row of DCT blocks.
279 */
280 for (block_row = 0; block_row < block_rows; block_row++) {
281 thisblockrow = buffer[block_row];
282 (*cinfo->fdct->forward_DCT) (cinfo, compptr,
283 input_buf[ci], thisblockrow,
284 (JDIMENSION) (block_row * DCTSIZE),
285 (JDIMENSION) 0, blocks_across);
286 if (ndummy > 0) {
287 /* Create dummy blocks at the right edge of the image. */
288 thisblockrow += blocks_across; /* => first dummy block */
289 jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
290 lastDC = thisblockrow[-1][0];
291 for (bi = 0; bi < ndummy; bi++) {
292 thisblockrow[bi][0] = lastDC;
293 }
294 }
295 }
296 /* If at end of image, create dummy block rows as needed.
297 * The tricky part here is that within each MCU, we want the DC values
298 * of the dummy blocks to match the last real block's DC value.
299 * This squeezes a few more bytes out of the resulting file...
300 */
301 if (coef->iMCU_row_num == last_iMCU_row) {
302 blocks_across += ndummy; /* include lower right corner */
303 MCUs_across = blocks_across / h_samp_factor;
304 for (block_row = block_rows; block_row < compptr->v_samp_factor;
305 block_row++) {
306 thisblockrow = buffer[block_row];
307 lastblockrow = buffer[block_row-1];
308 jzero_far((void FAR *) thisblockrow,
309 (size_t) (blocks_across * SIZEOF(JBLOCK)));
310 for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
311 lastDC = lastblockrow[h_samp_factor-1][0];
312 for (bi = 0; bi < h_samp_factor; bi++) {
313 thisblockrow[bi][0] = lastDC;
314 }
315 thisblockrow += h_samp_factor; /* advance to next MCU in row */
316 lastblockrow += h_samp_factor;
317 }
318 }
319 }
320 }
321 /* NB: compress_output will increment iMCU_row_num if successful.
322 * A suspension return will result in redoing all the work above next time.
323 */
324
325 /* Emit data to the entropy encoder, sharing code with subsequent passes */
326 return compress_output(cinfo, input_buf);
327}
328
329
330/*
331 * Process some data in subsequent passes of a multi-pass case.
332 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
333 * per call, ie, v_samp_factor block rows for each component in the scan.
334 * The data is obtained from the virtual arrays and fed to the entropy coder.
335 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
336 *
337 * NB: input_buf is ignored; it is likely to be a NULL pointer.
338 */
339
340METHODDEF(boolean)
341compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
342{
343 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
344 JDIMENSION MCU_col_num; /* index of current MCU within row */
345 int blkn, ci, xindex, yindex, yoffset;
346 JDIMENSION start_col;
347 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
348 JBLOCKROW buffer_ptr;
349 jpeg_component_info *compptr;
350
351 /* Align the virtual buffers for the components used in this scan.
352 * NB: during first pass, this is safe only because the buffers will
353 * already be aligned properly, so jmemmgr.c won't need to do any I/O.
354 */
355 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
356 compptr = cinfo->cur_comp_info[ci];
357 buffer[ci] = (*cinfo->mem->access_virt_barray)
358 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
359 coef->iMCU_row_num * compptr->v_samp_factor,
360 (JDIMENSION) compptr->v_samp_factor, FALSE);
361 }
362
363 /* Loop to process one whole iMCU row */
364 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
365 yoffset++) {
366 for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
367 MCU_col_num++) {
368 /* Construct list of pointers to DCT blocks belonging to this MCU */
369 blkn = 0; /* index of current DCT block within MCU */
370 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
371 compptr = cinfo->cur_comp_info[ci];
372 start_col = MCU_col_num * compptr->MCU_width;
373 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
374 buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
375 for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
376 coef->MCU_buffer[blkn++] = buffer_ptr++;
377 }
378 }
379 }
380 /* Try to write the MCU. */
381 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
382 /* Suspension forced; update state counters and exit */
383 coef->MCU_vert_offset = yoffset;
384 coef->mcu_ctr = MCU_col_num;
385 return FALSE;
386 }
387 }
388 /* Completed an MCU row, but perhaps not an iMCU row */
389 coef->mcu_ctr = 0;
390 }
391 /* Completed the iMCU row, advance counters for next one */
392 coef->iMCU_row_num++;
393 start_iMCU_row(cinfo);
394 return TRUE;
395}
396
397#endif /* FULL_COEF_BUFFER_SUPPORTED */
398
399
400/*
401 * Initialize coefficient buffer controller.
402 */
403
404GLOBAL(void)
405jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
406{
407 my_coef_ptr coef;
408
409 coef = (my_coef_ptr)
410 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
411 SIZEOF(my_coef_controller));
412 cinfo->coef = (struct jpeg_c_coef_controller *) coef;
413 coef->pub.start_pass = start_pass_coef;
414
415 /* Create the coefficient buffer. */
416 if (need_full_buffer) {
417#ifdef FULL_COEF_BUFFER_SUPPORTED
418 /* Allocate a full-image virtual array for each component, */
419 /* padded to a multiple of samp_factor DCT blocks in each direction. */
420 int ci;
421 jpeg_component_info *compptr;
422
423 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
424 ci++, compptr++) {
425 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
426 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
427 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
428 (long) compptr->h_samp_factor),
429 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
430 (long) compptr->v_samp_factor),
431 (JDIMENSION) compptr->v_samp_factor);
432 }
433#else
434 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
435#endif
436 } else {
437 /* We only need a single-MCU buffer. */
438 JBLOCKROW buffer;
439 int i;
440
441 buffer = (JBLOCKROW)
442 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
443 C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
444 for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
445 coef->MCU_buffer[i] = buffer + i;
446 }
447 coef->whole_image[0] = NULL; /* flag for no virtual arrays */
448 }
449}
450