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 } 455
