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 } 450
