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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
 *
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 * This file contains the coefficient buffer controller for compression.
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 * This controller is the top level of the JPEG compressor proper.
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 * The coefficient buffer lies between forward-DCT and entropy encoding steps.
11
 */
12

13
#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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17

18
/* We use a full-image coefficient buffer when doing Huffman optimization,
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 * and also for writing multiple-scan JPEG files.  In all cases, the DCT
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 * step is run during the first pass, and subsequent passes need only read
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 * the buffered coefficients.
22
 */
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#ifdef ENTROPY_OPT_SUPPORTED
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#define FULL_COEF_BUFFER_SUPPORTED
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#else
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#ifdef C_MULTISCAN_FILES_SUPPORTED
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#define FULL_COEF_BUFFER_SUPPORTED
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#endif
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#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 */
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  int MCU_vert_offset;		/* counts MCU rows within iMCU row */
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  int MCU_rows_per_iMCU_row;	/* number of such rows needed */
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  /* For single-pass compression, it's sufficient to buffer just one MCU
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   * (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
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   * it's not really very big; this is to keep the module interfaces unchanged
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   * when a large coefficient buffer is necessary.)
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   * In multi-pass modes, this array points to the current MCU's blocks
49
   * within the virtual arrays.
50
   */
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  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));
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#ifdef FULL_COEF_BUFFER_SUPPORTED
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METHODDEF(boolean) compress_first_pass
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    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
66
METHODDEF(boolean) compress_output
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    JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
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#endif
69

70

71
LOCAL(void)
72
start_iMCU_row (j_compress_ptr cinfo)
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/* Reset within-iMCU-row counters for a new row */
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{
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  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.
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   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
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   * 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))
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      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
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    else
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      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
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  }
89

90
  coef->mcu_ctr = 0;
91
  coef->MCU_vert_offset = 0;
92
}
93

94

95
/*
96
 * Initialize for a processing pass.
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 */
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;
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    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);
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    coef->pub.compress_data = compress_output;
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    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;
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	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],
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					 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

451