src/jpeg/jccoefct.c

   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(wxjpeg_boolean) compress_data
  62     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
  63 #ifdef FULL_COEF_BUFFER_SUPPORTED
  64 METHODDEF(wxjpeg_boolean) compress_first_pass
  65     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
  66 METHODDEF(wxjpeg_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(wxjpeg_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(wxjpeg_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(wxjpeg_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, wxjpeg_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 }