1 /* 2 * jccoefct.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1994-1997, Thomas G. Lane. 6 * It was modified by The libjpeg-turbo Project to include only code and 7 * information relevant to libjpeg-turbo. 8 * For conditions of distribution and use, see the accompanying README file. 9 * 10 * This file contains the coefficient buffer controller for compression. 11 * This controller is the top level of the JPEG compressor proper. 12 * The coefficient buffer lies between forward-DCT and entropy encoding steps. 13 */ 14 15 #define JPEG_INTERNALS 16 #include "jinclude.h" 17 #include "jpeglib.h" 18 19 20 /* We use a full-image coefficient buffer when doing Huffman optimization, 21 * and also for writing multiple-scan JPEG files. In all cases, the DCT 22 * step is run during the first pass, and subsequent passes need only read 23 * the buffered coefficients. 24 */ 25 #ifdef ENTROPY_OPT_SUPPORTED 26 #define FULL_COEF_BUFFER_SUPPORTED 27 #else 28 #ifdef C_MULTISCAN_FILES_SUPPORTED 29 #define FULL_COEF_BUFFER_SUPPORTED 30 #endif 31 #endif 32 33 34 /* Private buffer controller object */ 35 36 typedef struct { 37 struct jpeg_c_coef_controller pub; /* public fields */ 38 39 JDIMENSION iMCU_row_num; /* iMCU row # within image */ 40 JDIMENSION mcu_ctr; /* counts MCUs processed in current row */ 41 int MCU_vert_offset; /* counts MCU rows within iMCU row */ 42 int MCU_rows_per_iMCU_row; /* number of such rows needed */ 43 44 /* For single-pass compression, it's sufficient to buffer just one MCU 45 * (although this may prove a bit slow in practice). We allocate a 46 * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each 47 * MCU constructed and sent. In multi-pass modes, this array points to the 48 * current MCU's blocks within the virtual arrays. 49 */ 50 JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU]; 51 52 /* In multi-pass modes, we need a virtual block array for each component. */ 53 jvirt_barray_ptr whole_image[MAX_COMPONENTS]; 54 } my_coef_controller; 55 56 typedef my_coef_controller * my_coef_ptr; 57 58 59 /* Forward declarations */ 60 METHODDEF(boolean) compress_data 61 (j_compress_ptr cinfo, JSAMPIMAGE input_buf); 62 #ifdef FULL_COEF_BUFFER_SUPPORTED 63 METHODDEF(boolean) compress_first_pass 64 (j_compress_ptr cinfo, JSAMPIMAGE input_buf); 65 METHODDEF(boolean) compress_output 66 (j_compress_ptr cinfo, JSAMPIMAGE input_buf); 67 #endif 68 69 70 LOCAL(void) 71 start_iMCU_row (j_compress_ptr cinfo) 72 /* Reset within-iMCU-row counters for a new row */ 73 { 74 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; 75 76 /* In an interleaved scan, an MCU row is the same as an iMCU row. 77 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows. 78 * But at the bottom of the image, process only what's left. 79 */ 80 if (cinfo->comps_in_scan > 1) { 81 coef->MCU_rows_per_iMCU_row = 1; 82 } else { 83 if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1)) 84 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor; 85 else 86 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height; 87 } 88 89 coef->mcu_ctr = 0; 90 coef->MCU_vert_offset = 0; 91 } 92 93 94 /* 95 * Initialize for a processing pass. 96 */ 97 98 METHODDEF(void) 99 start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode) 100 { 101 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; 102 103 coef->iMCU_row_num = 0; 104 start_iMCU_row(cinfo); 105 106 switch (pass_mode) { 107 case JBUF_PASS_THRU: 108 if (coef->whole_image[0] != NULL) 109 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 110 coef->pub.compress_data = compress_data; 111 break; 112 #ifdef FULL_COEF_BUFFER_SUPPORTED 113 case JBUF_SAVE_AND_PASS: 114 if (coef->whole_image[0] == NULL) 115 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 116 coef->pub.compress_data = compress_first_pass; 117 break; 118 case JBUF_CRANK_DEST: 119 if (coef->whole_image[0] == NULL) 120 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 121 coef->pub.compress_data = compress_output; 122 break; 123 #endif 124 default: 125 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 126 break; 127 } 128 } 129 130 131 /* 132 * Process some data in the single-pass case. 133 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) 134 * per call, ie, v_samp_factor block rows for each component in the image. 135 * Returns TRUE if the iMCU row is completed, FALSE if suspended. 136 * 137 * NB: input_buf contains a plane for each component in image, 138 * which we index according to the component's SOF position. 139 */ 140 141 METHODDEF(boolean) 142 compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf) 143 { 144 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; 145 JDIMENSION MCU_col_num; /* index of current MCU within row */ 146 JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1; 147 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1; 148 int blkn, bi, ci, yindex, yoffset, blockcnt; 149 JDIMENSION ypos, xpos; 150 jpeg_component_info *compptr; 151 152 /* Loop to write as much as one whole iMCU row */ 153 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; 154 yoffset++) { 155 for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col; 156 MCU_col_num++) { 157 /* Determine where data comes from in input_buf and do the DCT thing. 158 * Each call on forward_DCT processes a horizontal row of DCT blocks 159 * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks 160 * sequentially. Dummy blocks at the right or bottom edge are filled in 161 * specially. The data in them does not matter for image reconstruction, 162 * so we fill them with values that will encode to the smallest amount of 163 * data, viz: all zeroes in the AC entries, DC entries equal to previous 164 * block's DC value. (Thanks to Thomas Kinsman for this idea.) 165 */ 166 blkn = 0; 167 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 168 compptr = cinfo->cur_comp_info[ci]; 169 blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width 170 : compptr->last_col_width; 171 xpos = MCU_col_num * compptr->MCU_sample_width; 172 ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */ 173 for (yindex = 0; yindex < compptr->MCU_height; yindex++) { 174 if (coef->iMCU_row_num < last_iMCU_row || 175 yoffset+yindex < compptr->last_row_height) { 176 (*cinfo->fdct->forward_DCT) (cinfo, compptr, 177 input_buf[compptr->component_index], 178 coef->MCU_buffer[blkn], 179 ypos, xpos, (JDIMENSION) blockcnt); 180 if (blockcnt < compptr->MCU_width) { 181 /* Create some dummy blocks at the right edge of the image. */ 182 jzero_far((void *) coef->MCU_buffer[blkn + blockcnt], 183 (compptr->MCU_width - blockcnt) * sizeof(JBLOCK)); 184 for (bi = blockcnt; bi < compptr->MCU_width; bi++) { 185 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0]; 186 } 187 } 188 } else { 189 /* Create a row of dummy blocks at the bottom of the image. */ 190 jzero_far((void *) coef->MCU_buffer[blkn], 191 compptr->MCU_width * sizeof(JBLOCK)); 192 for (bi = 0; bi < compptr->MCU_width; bi++) { 193 coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0]; 194 } 195 } 196 blkn += compptr->MCU_width; 197 ypos += DCTSIZE; 198 } 199 } 200 /* Try to write the MCU. In event of a suspension failure, we will 201 * re-DCT the MCU on restart (a bit inefficient, could be fixed...) 202 */ 203 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) { 204 /* Suspension forced; update state counters and exit */ 205 coef->MCU_vert_offset = yoffset; 206 coef->mcu_ctr = MCU_col_num; 207 return FALSE; 208 } 209 } 210 /* Completed an MCU row, but perhaps not an iMCU row */ 211 coef->mcu_ctr = 0; 212 } 213 /* Completed the iMCU row, advance counters for next one */ 214 coef->iMCU_row_num++; 215 start_iMCU_row(cinfo); 216 return TRUE; 217 } 218 219 220 #ifdef FULL_COEF_BUFFER_SUPPORTED 221 222 /* 223 * Process some data in the first pass of a multi-pass case. 224 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) 225 * per call, ie, v_samp_factor block rows for each component in the image. 226 * This amount of data is read from the source buffer, DCT'd and quantized, 227 * and saved into the virtual arrays. We also generate suitable dummy blocks 228 * as needed at the right and lower edges. (The dummy blocks are constructed 229 * in the virtual arrays, which have been padded appropriately.) This makes 230 * it possible for subsequent passes not to worry about real vs. dummy blocks. 231 * 232 * We must also emit the data to the entropy encoder. This is conveniently 233 * done by calling compress_output() after we've loaded the current strip 234 * of the virtual arrays. 235 * 236 * NB: input_buf contains a plane for each component in image. All 237 * components are DCT'd and loaded into the virtual arrays in this pass. 238 * However, it may be that only a subset of the components are emitted to 239 * the entropy encoder during this first pass; be careful about looking 240 * at the scan-dependent variables (MCU dimensions, etc). 241 */ 242 243 METHODDEF(boolean) 244 compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf) 245 { 246 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; 247 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1; 248 JDIMENSION blocks_across, MCUs_across, MCUindex; 249 int bi, ci, h_samp_factor, block_row, block_rows, ndummy; 250 JCOEF lastDC; 251 jpeg_component_info *compptr; 252 JBLOCKARRAY buffer; 253 JBLOCKROW thisblockrow, lastblockrow; 254 255 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 256 ci++, compptr++) { 257 /* Align the virtual buffer for this component. */ 258 buffer = (*cinfo->mem->access_virt_barray) 259 ((j_common_ptr) cinfo, coef->whole_image[ci], 260 coef->iMCU_row_num * compptr->v_samp_factor, 261 (JDIMENSION) compptr->v_samp_factor, TRUE); 262 /* Count non-dummy DCT block rows in this iMCU row. */ 263 if (coef->iMCU_row_num < last_iMCU_row) 264 block_rows = compptr->v_samp_factor; 265 else { 266 /* NB: can't use last_row_height here, since may not be set! */ 267 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor); 268 if (block_rows == 0) block_rows = compptr->v_samp_factor; 269 } 270 blocks_across = compptr->width_in_blocks; 271 h_samp_factor = compptr->h_samp_factor; 272 /* Count number of dummy blocks to be added at the right margin. */ 273 ndummy = (int) (blocks_across % h_samp_factor); 274 if (ndummy > 0) 275 ndummy = h_samp_factor - ndummy; 276 /* Perform DCT for all non-dummy blocks in this iMCU row. Each call 277 * on forward_DCT processes a complete horizontal row of DCT blocks. 278 */ 279 for (block_row = 0; block_row < block_rows; block_row++) { 280 thisblockrow = buffer[block_row]; 281 (*cinfo->fdct->forward_DCT) (cinfo, compptr, 282 input_buf[ci], thisblockrow, 283 (JDIMENSION) (block_row * DCTSIZE), 284 (JDIMENSION) 0, blocks_across); 285 if (ndummy > 0) { 286 /* Create dummy blocks at the right edge of the image. */ 287 thisblockrow += blocks_across; /* => first dummy block */ 288 jzero_far((void *) thisblockrow, ndummy * sizeof(JBLOCK)); 289 lastDC = thisblockrow[-1][0]; 290 for (bi = 0; bi < ndummy; bi++) { 291 thisblockrow[bi][0] = lastDC; 292 } 293 } 294 } 295 /* If at end of image, create dummy block rows as needed. 296 * The tricky part here is that within each MCU, we want the DC values 297 * of the dummy blocks to match the last real block's DC value. 298 * This squeezes a few more bytes out of the resulting file... 299 */ 300 if (coef->iMCU_row_num == last_iMCU_row) { 301 blocks_across += ndummy; /* include lower right corner */ 302 MCUs_across = blocks_across / h_samp_factor; 303 for (block_row = block_rows; block_row < compptr->v_samp_factor; 304 block_row++) { 305 thisblockrow = buffer[block_row]; 306 lastblockrow = buffer[block_row-1]; 307 jzero_far((void *) thisblockrow, 308 (size_t) (blocks_across * sizeof(JBLOCK))); 309 for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) { 310 lastDC = lastblockrow[h_samp_factor-1][0]; 311 for (bi = 0; bi < h_samp_factor; bi++) { 312 thisblockrow[bi][0] = lastDC; 313 } 314 thisblockrow += h_samp_factor; /* advance to next MCU in row */ 315 lastblockrow += h_samp_factor; 316 } 317 } 318 } 319 } 320 /* NB: compress_output will increment iMCU_row_num if successful. 321 * A suspension return will result in redoing all the work above next time. 322 */ 323 324 /* Emit data to the entropy encoder, sharing code with subsequent passes */ 325 return compress_output(cinfo, input_buf); 326 } 327 328 329 /* 330 * Process some data in subsequent passes of a multi-pass case. 331 * We process the equivalent of one fully interleaved MCU row ("iMCU" row) 332 * per call, ie, v_samp_factor block rows for each component in the scan. 333 * The data is obtained from the virtual arrays and fed to the entropy coder. 334 * Returns TRUE if the iMCU row is completed, FALSE if suspended. 335 * 336 * NB: input_buf is ignored; it is likely to be a NULL pointer. 337 */ 338 339 METHODDEF(boolean) 340 compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf) 341 { 342 my_coef_ptr coef = (my_coef_ptr) cinfo->coef; 343 JDIMENSION MCU_col_num; /* index of current MCU within row */ 344 int blkn, ci, xindex, yindex, yoffset; 345 JDIMENSION start_col; 346 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN]; 347 JBLOCKROW buffer_ptr; 348 jpeg_component_info *compptr; 349 350 /* Align the virtual buffers for the components used in this scan. 351 * NB: during first pass, this is safe only because the buffers will 352 * already be aligned properly, so jmemmgr.c won't need to do any I/O. 353 */ 354 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 355 compptr = cinfo->cur_comp_info[ci]; 356 buffer[ci] = (*cinfo->mem->access_virt_barray) 357 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index], 358 coef->iMCU_row_num * compptr->v_samp_factor, 359 (JDIMENSION) compptr->v_samp_factor, FALSE); 360 } 361 362 /* Loop to process one whole iMCU row */ 363 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; 364 yoffset++) { 365 for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row; 366 MCU_col_num++) { 367 /* Construct list of pointers to DCT blocks belonging to this MCU */ 368 blkn = 0; /* index of current DCT block within MCU */ 369 for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 370 compptr = cinfo->cur_comp_info[ci]; 371 start_col = MCU_col_num * compptr->MCU_width; 372 for (yindex = 0; yindex < compptr->MCU_height; yindex++) { 373 buffer_ptr = buffer[ci][yindex+yoffset] + start_col; 374 for (xindex = 0; xindex < compptr->MCU_width; xindex++) { 375 coef->MCU_buffer[blkn++] = buffer_ptr++; 376 } 377 } 378 } 379 /* Try to write the MCU. */ 380 if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) { 381 /* Suspension forced; update state counters and exit */ 382 coef->MCU_vert_offset = yoffset; 383 coef->mcu_ctr = MCU_col_num; 384 return FALSE; 385 } 386 } 387 /* Completed an MCU row, but perhaps not an iMCU row */ 388 coef->mcu_ctr = 0; 389 } 390 /* Completed the iMCU row, advance counters for next one */ 391 coef->iMCU_row_num++; 392 start_iMCU_row(cinfo); 393 return TRUE; 394 } 395 396 #endif /* FULL_COEF_BUFFER_SUPPORTED */ 397 398 399 /* 400 * Initialize coefficient buffer controller. 401 */ 402 403 GLOBAL(void) 404 jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer) 405 { 406 my_coef_ptr coef; 407 408 coef = (my_coef_ptr) 409 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 410 sizeof(my_coef_controller)); 411 cinfo->coef = (struct jpeg_c_coef_controller *) coef; 412 coef->pub.start_pass = start_pass_coef; 413 414 /* Create the coefficient buffer. */ 415 if (need_full_buffer) { 416 #ifdef FULL_COEF_BUFFER_SUPPORTED 417 /* Allocate a full-image virtual array for each component, */ 418 /* padded to a multiple of samp_factor DCT blocks in each direction. */ 419 int ci; 420 jpeg_component_info *compptr; 421 422 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 423 ci++, compptr++) { 424 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray) 425 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE, 426 (JDIMENSION) jround_up((long) compptr->width_in_blocks, 427 (long) compptr->h_samp_factor), 428 (JDIMENSION) jround_up((long) compptr->height_in_blocks, 429 (long) compptr->v_samp_factor), 430 (JDIMENSION) compptr->v_samp_factor); 431 } 432 #else 433 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE); 434 #endif 435 } else { 436 /* We only need a single-MCU buffer. */ 437 JBLOCKROW buffer; 438 int i; 439 440 buffer = (JBLOCKROW) 441 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE, 442 C_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK)); 443 for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) { 444 coef->MCU_buffer[i] = buffer + i; 445 } 446 coef->whole_image[0] = NULL; /* flag for no virtual arrays */ 447 } 448 } 449
