summaryrefslogtreecommitdiff
path: root/src/jpeg-8c/jcprepct.c
blob: be44cc4b4511d08383b776d4a36431c6b6e8f1cd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
/*
 * jcprepct.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the compression preprocessing controller.
 * This controller manages the color conversion, downsampling,
 * and edge expansion steps.
 *
 * Most of the complexity here is associated with buffering input rows
 * as required by the downsampler.  See the comments at the head of
 * jcsample.c for the downsampler's needs.
 */

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


/* At present, jcsample.c can request context rows only for smoothing.
 * In the future, we might also need context rows for CCIR601 sampling
 * or other more-complex downsampling procedures.  The code to support
 * context rows should be compiled only if needed.
 */
#ifdef INPUT_SMOOTHING_SUPPORTED
#define CONTEXT_ROWS_SUPPORTED
#endif


/*
 * For the simple (no-context-row) case, we just need to buffer one
 * row group's worth of pixels for the downsampling step.  At the bottom of
 * the image, we pad to a full row group by replicating the last pixel row.
 * The downsampler's last output row is then replicated if needed to pad
 * out to a full iMCU row.
 *
 * When providing context rows, we must buffer three row groups' worth of
 * pixels.  Three row groups are physically allocated, but the row pointer
 * arrays are made five row groups high, with the extra pointers above and
 * below "wrapping around" to point to the last and first real row groups.
 * This allows the downsampler to access the proper context rows.
 * At the top and bottom of the image, we create dummy context rows by
 * copying the first or last real pixel row.  This copying could be avoided
 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
 * trouble on the compression side.
 */


/* Private buffer controller object */

typedef struct {
  struct jpeg_c_prep_controller pub; /* public fields */

  /* Downsampling input buffer.  This buffer holds color-converted data
   * until we have enough to do a downsample step.
   */
  JSAMPARRAY color_buf[MAX_COMPONENTS];

  JDIMENSION rows_to_go;	/* counts rows remaining in source image */
  int next_buf_row;		/* index of next row to store in color_buf */

#ifdef CONTEXT_ROWS_SUPPORTED	/* only needed for context case */
  int this_row_group;		/* starting row index of group to process */
  int next_buf_stop;		/* downsample when we reach this index */
#endif
} my_prep_controller;

typedef my_prep_controller * my_prep_ptr;


/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

  if (pass_mode != JBUF_PASS_THRU)
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

  /* Initialize total-height counter for detecting bottom of image */
  prep->rows_to_go = cinfo->image_height;
  /* Mark the conversion buffer empty */
  prep->next_buf_row = 0;
#ifdef CONTEXT_ROWS_SUPPORTED
  /* Preset additional state variables for context mode.
   * These aren't used in non-context mode, so we needn't test which mode.
   */
  prep->this_row_group = 0;
  /* Set next_buf_stop to stop after two row groups have been read in. */
  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
#endif
}


/*
 * Expand an image vertically from height input_rows to height output_rows,
 * by duplicating the bottom row.
 */

LOCAL(void)
expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
		    int input_rows, int output_rows)
{
  register int row;

  for (row = input_rows; row < output_rows; row++) {
    jcopy_sample_rows(image_data, input_rows-1, image_data, row,
		      1, num_cols);
  }
}


/*
 * Process some data in the simple no-context case.
 *
 * Preprocessor output data is counted in "row groups".  A row group
 * is defined to be v_samp_factor sample rows of each component.
 * Downsampling will produce this much data from each max_v_samp_factor
 * input rows.
 */

METHODDEF(void)
pre_process_data (j_compress_ptr cinfo,
		  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
		  JDIMENSION in_rows_avail,
		  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
		  JDIMENSION out_row_groups_avail)
{
  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
  int numrows, ci;
  JDIMENSION inrows;
  jpeg_component_info * compptr;

  while (*in_row_ctr < in_rows_avail &&
	 *out_row_group_ctr < out_row_groups_avail) {
    /* Do color conversion to fill the conversion buffer. */
    inrows = in_rows_avail - *in_row_ctr;
    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
    numrows = (int) MIN((JDIMENSION) numrows, inrows);
    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
				       prep->color_buf,
				       (JDIMENSION) prep->next_buf_row,
				       numrows);
    *in_row_ctr += numrows;
    prep->next_buf_row += numrows;
    prep->rows_to_go -= numrows;
    /* If at bottom of image, pad to fill the conversion buffer. */
    if (prep->rows_to_go == 0 &&
	prep->next_buf_row < cinfo->max_v_samp_factor) {
      for (ci = 0; ci < cinfo->num_components; ci++) {
	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
			   prep->next_buf_row, cinfo->max_v_samp_factor);
      }
      prep->next_buf_row = cinfo->max_v_samp_factor;
    }
    /* If we've filled the conversion buffer, empty it. */
    if (prep->next_buf_row == cinfo->max_v_samp_factor) {
      (*cinfo->downsample->downsample) (cinfo,
					prep->color_buf, (JDIMENSION) 0,
					output_buf, *out_row_group_ctr);
      prep->next_buf_row = 0;
      (*out_row_group_ctr)++;
    }
    /* If at bottom of image, pad the output to a full iMCU height.
     * Note we assume the caller is providing a one-iMCU-height output buffer!
     */
    if (prep->rows_to_go == 0 &&
	*out_row_group_ctr < out_row_groups_avail) {
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	   ci++, compptr++) {
	numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
		  cinfo->min_DCT_v_scaled_size;
	expand_bottom_edge(output_buf[ci],
			   compptr->width_in_blocks * compptr->DCT_h_scaled_size,
			   (int) (*out_row_group_ctr * numrows),
			   (int) (out_row_groups_avail * numrows));
      }
      *out_row_group_ctr = out_row_groups_avail;
      break;			/* can exit outer loop without test */
    }
  }
}


#ifdef CONTEXT_ROWS_SUPPORTED

/*
 * Process some data in the context case.
 */

METHODDEF(void)
pre_process_context (j_compress_ptr cinfo,
		     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
		     JDIMENSION in_rows_avail,
		     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
		     JDIMENSION out_row_groups_avail)
{
  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
  int numrows, ci;
  int buf_height = cinfo->max_v_samp_factor * 3;
  JDIMENSION inrows;

  while (*out_row_group_ctr < out_row_groups_avail) {
    if (*in_row_ctr < in_rows_avail) {
      /* Do color conversion to fill the conversion buffer. */
      inrows = in_rows_avail - *in_row_ctr;
      numrows = prep->next_buf_stop - prep->next_buf_row;
      numrows = (int) MIN((JDIMENSION) numrows, inrows);
      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
					 prep->color_buf,
					 (JDIMENSION) prep->next_buf_row,
					 numrows);
      /* Pad at top of image, if first time through */
      if (prep->rows_to_go == cinfo->image_height) {
	for (ci = 0; ci < cinfo->num_components; ci++) {
	  int row;
	  for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
	    jcopy_sample_rows(prep->color_buf[ci], 0,
			      prep->color_buf[ci], -row,
			      1, cinfo->image_width);
	  }
	}
      }
      *in_row_ctr += numrows;
      prep->next_buf_row += numrows;
      prep->rows_to_go -= numrows;
    } else {
      /* Return for more data, unless we are at the bottom of the image. */
      if (prep->rows_to_go != 0)
	break;
      /* When at bottom of image, pad to fill the conversion buffer. */
      if (prep->next_buf_row < prep->next_buf_stop) {
	for (ci = 0; ci < cinfo->num_components; ci++) {
	  expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
			     prep->next_buf_row, prep->next_buf_stop);
	}
	prep->next_buf_row = prep->next_buf_stop;
      }
    }
    /* If we've gotten enough data, downsample a row group. */
    if (prep->next_buf_row == prep->next_buf_stop) {
      (*cinfo->downsample->downsample) (cinfo,
					prep->color_buf,
					(JDIMENSION) prep->this_row_group,
					output_buf, *out_row_group_ctr);
      (*out_row_group_ctr)++;
      /* Advance pointers with wraparound as necessary. */
      prep->this_row_group += cinfo->max_v_samp_factor;
      if (prep->this_row_group >= buf_height)
	prep->this_row_group = 0;
      if (prep->next_buf_row >= buf_height)
	prep->next_buf_row = 0;
      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
    }
  }
}


/*
 * Create the wrapped-around downsampling input buffer needed for context mode.
 */

LOCAL(void)
create_context_buffer (j_compress_ptr cinfo)
{
  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
  int rgroup_height = cinfo->max_v_samp_factor;
  int ci, i;
  jpeg_component_info * compptr;
  JSAMPARRAY true_buffer, fake_buffer;

  /* Grab enough space for fake row pointers for all the components;
   * we need five row groups' worth of pointers for each component.
   */
  fake_buffer = (JSAMPARRAY)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				(cinfo->num_components * 5 * rgroup_height) *
				SIZEOF(JSAMPROW));

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Allocate the actual buffer space (3 row groups) for this component.
     * We make the buffer wide enough to allow the downsampler to edge-expand
     * horizontally within the buffer, if it so chooses.
     */
    true_buffer = (*cinfo->mem->alloc_sarray)
      ((j_common_ptr) cinfo, JPOOL_IMAGE,
       (JDIMENSION) (((long) compptr->width_in_blocks *
		      cinfo->min_DCT_h_scaled_size *
		      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
       (JDIMENSION) (3 * rgroup_height));
    /* Copy true buffer row pointers into the middle of the fake row array */
    MEMCOPY(fake_buffer + rgroup_height, true_buffer,
	    3 * rgroup_height * SIZEOF(JSAMPROW));
    /* Fill in the above and below wraparound pointers */
    for (i = 0; i < rgroup_height; i++) {
      fake_buffer[i] = true_buffer[2 * rgroup_height + i];
      fake_buffer[4 * rgroup_height + i] = true_buffer[i];
    }
    prep->color_buf[ci] = fake_buffer + rgroup_height;
    fake_buffer += 5 * rgroup_height; /* point to space for next component */
  }
}

#endif /* CONTEXT_ROWS_SUPPORTED */


/*
 * Initialize preprocessing controller.
 */

GLOBAL(void)
jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
{
  my_prep_ptr prep;
  int ci;
  jpeg_component_info * compptr;

  if (need_full_buffer)		/* safety check */
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

  prep = (my_prep_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_prep_controller));
  cinfo->prep = (struct jpeg_c_prep_controller *) prep;
  prep->pub.start_pass = start_pass_prep;

  /* Allocate the color conversion buffer.
   * We make the buffer wide enough to allow the downsampler to edge-expand
   * horizontally within the buffer, if it so chooses.
   */
  if (cinfo->downsample->need_context_rows) {
    /* Set up to provide context rows */
#ifdef CONTEXT_ROWS_SUPPORTED
    prep->pub.pre_process_data = pre_process_context;
    create_context_buffer(cinfo);
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
  } else {
    /* No context, just make it tall enough for one row group */
    prep->pub.pre_process_data = pre_process_data;
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	 (JDIMENSION) (((long) compptr->width_in_blocks *
			cinfo->min_DCT_h_scaled_size *
			cinfo->max_h_samp_factor) / compptr->h_samp_factor),
	 (JDIMENSION) cinfo->max_v_samp_factor);
    }
  }
}