1 /*
2 * jccoefct.c
3 *
4 * Copyright (C) 1994-1997, Thomas G. Lane.
5 * Modified 2003-2011 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This file contains the coefficient buffer controller for compression.
10 * This controller is the top level of the JPEG compressor proper.
11 * The coefficient buffer lies between forward-DCT and entropy encoding steps.
12 */
13
14 #define JPEG_INTERNALS
15 #include "jinclude.h"
16 #include "jpeglib.h"
17
18
19 /* We use a full-image coefficient buffer when doing Huffman optimization,
20 * and also for writing multiple-scan JPEG files. In all cases, the DCT
21 * step is run during the first pass, and subsequent passes need only read
22 * the buffered coefficients.
23 */
24 #ifdef ENTROPY_OPT_SUPPORTED
25 #define FULL_COEF_BUFFER_SUPPORTED
26 #else
27 #ifdef C_MULTISCAN_FILES_SUPPORTED
28 #define FULL_COEF_BUFFER_SUPPORTED
29 #endif
30 #endif
31
32
33 /* Private buffer controller object */
34
35 typedef struct {
36 struct jpeg_c_coef_controller pub; /* public fields */
37
38 JDIMENSION iMCU_row_num; /* iMCU row # within image */
39 JDIMENSION mcu_ctr; /* counts MCUs processed in current row */
40 int MCU_vert_offset; /* counts MCU rows within iMCU row */
41 int MCU_rows_per_iMCU_row; /* number of such rows needed */
42
43 /* For single-pass compression, it's sufficient to buffer just one MCU
44 * (although this may prove a bit slow in practice). We allocate a
45 * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
46 * MCU constructed and sent. (On 80x86, the workspace is FAR even though
47 * it's not really very big; this is to keep the module interfaces unchanged
48 * when a large coefficient buffer is necessary.)
49 * In multi-pass modes, this array points to the current MCU's blocks
50 * within the virtual arrays.
51 */
52 JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
53
54 /* In multi-pass modes, we need a virtual block array for each component. */
55 jvirt_barray_ptr whole_image[MAX_COMPONENTS];
56 } my_coef_controller;
57
58 typedef my_coef_controller * my_coef_ptr;
59
60
61 /* Forward declarations */
62 METHODDEF(boolean) compress_data
63 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
64 #ifdef FULL_COEF_BUFFER_SUPPORTED
65 METHODDEF(boolean) compress_first_pass
66 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
67 METHODDEF(boolean) compress_output
68 JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
69 #endif
70
71
72 LOCAL(void)
73 start_iMCU_row (j_compress_ptr cinfo)
74 /* Reset within-iMCU-row counters for a new row */
75 {
76 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
77
78 /* In an interleaved scan, an MCU row is the same as an iMCU row.
79 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
80 * But at the bottom of the image, process only what's left.
81 */
82 if (cinfo->comps_in_scan > 1) {
83 coef->MCU_rows_per_iMCU_row = 1;
84 } else {
85 if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
86 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
87 else
88 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
89 }
90
91 coef->mcu_ctr = 0;
92 coef->MCU_vert_offset = 0;
93 }
94
95
96 /*
97 * Initialize for a processing pass.
98 */
99
100 METHODDEF(void)
101 start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
102 {
103 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
104
105 coef->iMCU_row_num = 0;
106 start_iMCU_row(cinfo);
107
108 switch (pass_mode) {
109 case JBUF_PASS_THRU:
110 if (coef->whole_image[0] != NULL)
111 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
112 coef->pub.compress_data = compress_data;
113 break;
114 #ifdef FULL_COEF_BUFFER_SUPPORTED
115 case JBUF_SAVE_AND_PASS:
116 if (coef->whole_image[0] == NULL)
117 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
118 coef->pub.compress_data = compress_first_pass;
119 break;
120 case JBUF_CRANK_DEST:
121 if (coef->whole_image[0] == NULL)
122 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
123 coef->pub.compress_data = compress_output;
124 break;
125 #endif
126 default:
127 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
128 break;
129 }
130 }
131
132
133 /*
134 * Process some data in the single-pass case.
135 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
136 * per call, ie, v_samp_factor block rows for each component in the image.
137 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
138 *
139 * NB: input_buf contains a plane for each component in image,
140 * which we index according to the component's SOF position.
141 */
142
143 METHODDEF(boolean)
144 compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
145 {
146 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
147 JDIMENSION MCU_col_num; /* index of current MCU within row */
148 JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
149 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
150 int blkn, bi, ci, yindex, yoffset, blockcnt;
151 JDIMENSION ypos, xpos;
152 jpeg_component_info *compptr;
153 forward_DCT_ptr forward_DCT;
154
155 /* Loop to write as much as one whole iMCU row */
156 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
157 yoffset++) {
158 for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
159 MCU_col_num++) {
160 /* Determine where data comes from in input_buf and do the DCT thing.
161 * Each call on forward_DCT processes a horizontal row of DCT blocks
162 * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
163 * sequentially. Dummy blocks at the right or bottom edge are filled in
164 * specially. The data in them does not matter for image reconstruction,
165 * so we fill them with values that will encode to the smallest amount of
166 * data, viz: all zeroes in the AC entries, DC entries equal to previous
167 * block's DC value. (Thanks to Thomas Kinsman for this idea.)
168 */
169 blkn = 0;
170 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
171 compptr = cinfo->cur_comp_info[ci];
172 forward_DCT = cinfo->fdct->forward_DCT[compptr->component_index];
173 blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
174 : compptr->last_col_width;
175 xpos = MCU_col_num * compptr->MCU_sample_width;
176 ypos = yoffset * compptr->DCT_v_scaled_size;
177 /* 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 (*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 FMEMZERO((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 FMEMZERO((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 += compptr->DCT_v_scaled_size;
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
248 METHODDEF(boolean)
249 compress_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 forward_DCT_ptr forward_DCT;
260
261 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
262 ci++, compptr++) {
263 /* Align the virtual buffer for this component. */
264 buffer = (*cinfo->mem->access_virt_barray)
265 ((j_common_ptr) cinfo, coef->whole_image[ci],
266 coef->iMCU_row_num * compptr->v_samp_factor,
267 (JDIMENSION) compptr->v_samp_factor, TRUE);
268 /* Count non-dummy DCT block rows in this iMCU row. */
269 if (coef->iMCU_row_num < last_iMCU_row)
270 block_rows = compptr->v_samp_factor;
271 else {
272 /* NB: can't use last_row_height here, since may not be set! */
273 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
274 if (block_rows == 0) block_rows = compptr->v_samp_factor;
275 }
276 blocks_across = compptr->width_in_blocks;
277 h_samp_factor = compptr->h_samp_factor;
278 /* Count number of dummy blocks to be added at the right margin. */
279 ndummy = (int) (blocks_across % h_samp_factor);
280 if (ndummy > 0)
281 ndummy = h_samp_factor - ndummy;
282 forward_DCT = cinfo->fdct->forward_DCT[ci];
283 /* Perform DCT for all non-dummy blocks in this iMCU row. Each call
284 * on forward_DCT processes a complete horizontal row of DCT blocks.
285 */
286 for (block_row = 0; block_row < block_rows; block_row++) {
287 thisblockrow = buffer[block_row];
288 (*forward_DCT) (cinfo, compptr, input_buf[ci], thisblockrow,
289 (JDIMENSION) (block_row * compptr->DCT_v_scaled_size),
290 (JDIMENSION) 0, blocks_across);
291 if (ndummy > 0) {
292 /* Create dummy blocks at the right edge of the image. */
293 thisblockrow += blocks_across; /* => first dummy block */
294 FMEMZERO((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
295 lastDC = thisblockrow[-1][0];
296 for (bi = 0; bi < ndummy; bi++) {
297 thisblockrow[bi][0] = lastDC;
298 }
299 }
300 }
301 /* If at end of image, create dummy block rows as needed.
302 * The tricky part here is that within each MCU, we want the DC values
303 * of the dummy blocks to match the last real block's DC value.
304 * This squeezes a few more bytes out of the resulting file...
305 */
306 if (coef->iMCU_row_num == last_iMCU_row) {
307 blocks_across += ndummy; /* include lower right corner */
308 MCUs_across = blocks_across / h_samp_factor;
309 for (block_row = block_rows; block_row < compptr->v_samp_factor;
310 block_row++) {
311 thisblockrow = buffer[block_row];
312 lastblockrow = buffer[block_row-1];
313 FMEMZERO((void FAR *) thisblockrow,
314 (size_t) (blocks_across * SIZEOF(JBLOCK)));
315 for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
316 lastDC = lastblockrow[h_samp_factor-1][0];
317 for (bi = 0; bi < h_samp_factor; bi++) {
318 thisblockrow[bi][0] = lastDC;
319 }
320 thisblockrow += h_samp_factor; /* advance to next MCU in row */
321 lastblockrow += h_samp_factor;
322 }
323 }
324 }
325 }
326 /* NB: compress_output will increment iMCU_row_num if successful.
327 * A suspension return will result in redoing all the work above next time.
328 */
329
330 /* Emit data to the entropy encoder, sharing code with subsequent passes */
331 return compress_output(cinfo, input_buf);
332 }
333
334
335 /*
336 * Process some data in subsequent passes of a multi-pass case.
337 * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
338 * per call, ie, v_samp_factor block rows for each component in the scan.
339 * The data is obtained from the virtual arrays and fed to the entropy coder.
340 * Returns TRUE if the iMCU row is completed, FALSE if suspended.
341 *
342 * NB: input_buf is ignored; it is likely to be a NULL pointer.
343 */
344
345 METHODDEF(boolean)
346 compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
347 {
348 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
349 JDIMENSION MCU_col_num; /* index of current MCU within row */
350 int blkn, ci, xindex, yindex, yoffset;
351 JDIMENSION start_col;
352 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
353 JBLOCKROW buffer_ptr;
354 jpeg_component_info *compptr;
355
356 /* Align the virtual buffers for the components used in this scan.
357 * NB: during first pass, this is safe only because the buffers will
358 * already be aligned properly, so jmemmgr.c won't need to do any I/O.
359 */
360 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
361 compptr = cinfo->cur_comp_info[ci];
362 buffer[ci] = (*cinfo->mem->access_virt_barray)
363 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
364 coef->iMCU_row_num * compptr->v_samp_factor,
365 (JDIMENSION) compptr->v_samp_factor, FALSE);
366 }
367
368 /* Loop to process one whole iMCU row */
369 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
370 yoffset++) {
371 for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
372 MCU_col_num++) {
373 /* Construct list of pointers to DCT blocks belonging to this MCU */
374 blkn = 0; /* index of current DCT block within MCU */
375 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
376 compptr = cinfo->cur_comp_info[ci];
377 start_col = MCU_col_num * compptr->MCU_width;
378 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
379 buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
380 for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
381 coef->MCU_buffer[blkn++] = buffer_ptr++;
382 }
383 }
384 }
385 /* Try to write the MCU. */
386 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
387 /* Suspension forced; update state counters and exit */
388 coef->MCU_vert_offset = yoffset;
389 coef->mcu_ctr = MCU_col_num;
390 return FALSE;
391 }
392 }
393 /* Completed an MCU row, but perhaps not an iMCU row */
394 coef->mcu_ctr = 0;
395 }
396 /* Completed the iMCU row, advance counters for next one */
397 coef->iMCU_row_num++;
398 start_iMCU_row(cinfo);
399 return TRUE;
400 }
401
402 #endif /* FULL_COEF_BUFFER_SUPPORTED */
403
404
405 /*
406 * Initialize coefficient buffer controller.
407 */
408
409 GLOBAL(void)
410 jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
411 {
412 my_coef_ptr coef;
413
414 coef = (my_coef_ptr)
415 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
416 SIZEOF(my_coef_controller));
417 cinfo->coef = (struct jpeg_c_coef_controller *) coef;
418 coef->pub.start_pass = start_pass_coef;
419
420 /* Create the coefficient buffer. */
421 if (need_full_buffer) {
422 #ifdef FULL_COEF_BUFFER_SUPPORTED
423 /* Allocate a full-image virtual array for each component, */
424 /* padded to a multiple of samp_factor DCT blocks in each direction. */
425 int ci;
426 jpeg_component_info *compptr;
427
428 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
429 ci++, compptr++) {
430 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
431 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
432 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
433 (long) compptr->h_samp_factor),
434 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
435 (long) compptr->v_samp_factor),
436 (JDIMENSION) compptr->v_samp_factor);
437 }
438 #else
439 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
440 #endif
441 } else {
442 /* We only need a single-MCU buffer. */
443 JBLOCKROW buffer;
444 int i;
445
446 buffer = (JBLOCKROW)
447 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
448 C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
449 for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
450 coef->MCU_buffer[i] = buffer + i;
451 }
452 coef->whole_image[0] = NULL; /* flag for no virtual arrays */
453 }
454 }