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| 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 |
| 34 typedef 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 |
| 57 typedef my_coef_controller * my_coef_ptr; |
| 58 |
| 59 |
| 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)); |
| 68 #endif |
| 69 |
| 70 |
| 71 LOCAL(void) |
| 72 start_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 |
| 99 METHODDEF(void) |
| 100 start_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 |
| 142 METHODDEF(boolean) |
| 143 compress_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 |
| 244 METHODDEF(boolean) |
| 245 compress_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 |
| 340 METHODDEF(boolean) |
| 341 compress_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 |
| 404 GLOBAL(void) |
| 405 jinit_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 } |
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