source: trunk/libjpeg/jcprepct.c @ 283

Last change on this file since 283 was 283, checked in by rbri, 12 years ago

JPEG plugin: libjpeg updated to version 7

File size: 12.3 KB
Line 
1/*
2 * jcprepct.c
3 *
4 * Copyright (C) 1994-1996, 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 compression preprocessing controller.
9 * This controller manages the color conversion, downsampling,
10 * and edge expansion steps.
11 *
12 * Most of the complexity here is associated with buffering input rows
13 * as required by the downsampler.  See the comments at the head of
14 * jcsample.c for the downsampler's needs.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20
21
22/* At present, jcsample.c can request context rows only for smoothing.
23 * In the future, we might also need context rows for CCIR601 sampling
24 * or other more-complex downsampling procedures.  The code to support
25 * context rows should be compiled only if needed.
26 */
27#ifdef INPUT_SMOOTHING_SUPPORTED
28#define CONTEXT_ROWS_SUPPORTED
29#endif
30
31
32/*
33 * For the simple (no-context-row) case, we just need to buffer one
34 * row group's worth of pixels for the downsampling step.  At the bottom of
35 * the image, we pad to a full row group by replicating the last pixel row.
36 * The downsampler's last output row is then replicated if needed to pad
37 * out to a full iMCU row.
38 *
39 * When providing context rows, we must buffer three row groups' worth of
40 * pixels.  Three row groups are physically allocated, but the row pointer
41 * arrays are made five row groups high, with the extra pointers above and
42 * below "wrapping around" to point to the last and first real row groups.
43 * This allows the downsampler to access the proper context rows.
44 * At the top and bottom of the image, we create dummy context rows by
45 * copying the first or last real pixel row.  This copying could be avoided
46 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
47 * trouble on the compression side.
48 */
49
50
51/* Private buffer controller object */
52
53typedef struct {
54  struct jpeg_c_prep_controller pub; /* public fields */
55
56  /* Downsampling input buffer.  This buffer holds color-converted data
57   * until we have enough to do a downsample step.
58   */
59  JSAMPARRAY color_buf[MAX_COMPONENTS];
60
61  JDIMENSION rows_to_go;        /* counts rows remaining in source image */
62  int next_buf_row;             /* index of next row to store in color_buf */
63
64#ifdef CONTEXT_ROWS_SUPPORTED   /* only needed for context case */
65  int this_row_group;           /* starting row index of group to process */
66  int next_buf_stop;            /* downsample when we reach this index */
67#endif
68} my_prep_controller;
69
70typedef my_prep_controller * my_prep_ptr;
71
72
73/*
74 * Initialize for a processing pass.
75 */
76
77METHODDEF(void)
78start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
79{
80  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
81
82  if (pass_mode != JBUF_PASS_THRU)
83    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
84
85  /* Initialize total-height counter for detecting bottom of image */
86  prep->rows_to_go = cinfo->image_height;
87  /* Mark the conversion buffer empty */
88  prep->next_buf_row = 0;
89#ifdef CONTEXT_ROWS_SUPPORTED
90  /* Preset additional state variables for context mode.
91   * These aren't used in non-context mode, so we needn't test which mode.
92   */
93  prep->this_row_group = 0;
94  /* Set next_buf_stop to stop after two row groups have been read in. */
95  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
96#endif
97}
98
99
100/*
101 * Expand an image vertically from height input_rows to height output_rows,
102 * by duplicating the bottom row.
103 */
104
105LOCAL(void)
106expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
107                    int input_rows, int output_rows)
108{
109  register int row;
110
111  for (row = input_rows; row < output_rows; row++) {
112    jcopy_sample_rows(image_data, input_rows-1, image_data, row,
113                      1, num_cols);
114  }
115}
116
117
118/*
119 * Process some data in the simple no-context case.
120 *
121 * Preprocessor output data is counted in "row groups".  A row group
122 * is defined to be v_samp_factor sample rows of each component.
123 * Downsampling will produce this much data from each max_v_samp_factor
124 * input rows.
125 */
126
127METHODDEF(void)
128pre_process_data (j_compress_ptr cinfo,
129                  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
130                  JDIMENSION in_rows_avail,
131                  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
132                  JDIMENSION out_row_groups_avail)
133{
134  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
135  int numrows, ci;
136  JDIMENSION inrows;
137  jpeg_component_info * compptr;
138
139  while (*in_row_ctr < in_rows_avail &&
140         *out_row_group_ctr < out_row_groups_avail) {
141    /* Do color conversion to fill the conversion buffer. */
142    inrows = in_rows_avail - *in_row_ctr;
143    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
144    numrows = (int) MIN((JDIMENSION) numrows, inrows);
145    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
146                                       prep->color_buf,
147                                       (JDIMENSION) prep->next_buf_row,
148                                       numrows);
149    *in_row_ctr += numrows;
150    prep->next_buf_row += numrows;
151    prep->rows_to_go -= numrows;
152    /* If at bottom of image, pad to fill the conversion buffer. */
153    if (prep->rows_to_go == 0 &&
154        prep->next_buf_row < cinfo->max_v_samp_factor) {
155      for (ci = 0; ci < cinfo->num_components; ci++) {
156        expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
157                           prep->next_buf_row, cinfo->max_v_samp_factor);
158      }
159      prep->next_buf_row = cinfo->max_v_samp_factor;
160    }
161    /* If we've filled the conversion buffer, empty it. */
162    if (prep->next_buf_row == cinfo->max_v_samp_factor) {
163      (*cinfo->downsample->downsample) (cinfo,
164                                        prep->color_buf, (JDIMENSION) 0,
165                                        output_buf, *out_row_group_ctr);
166      prep->next_buf_row = 0;
167      (*out_row_group_ctr)++;
168    }
169    /* If at bottom of image, pad the output to a full iMCU height.
170     * Note we assume the caller is providing a one-iMCU-height output buffer!
171     */
172    if (prep->rows_to_go == 0 &&
173        *out_row_group_ctr < out_row_groups_avail) {
174      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
175           ci++, compptr++) {
176        numrows = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /
177                  cinfo->min_DCT_v_scaled_size;
178        expand_bottom_edge(output_buf[ci],
179                           compptr->width_in_blocks * compptr->DCT_h_scaled_size,
180                           (int) (*out_row_group_ctr * numrows),
181                           (int) (out_row_groups_avail * numrows));
182      }
183      *out_row_group_ctr = out_row_groups_avail;
184      break;                    /* can exit outer loop without test */
185    }
186  }
187}
188
189
190#ifdef CONTEXT_ROWS_SUPPORTED
191
192/*
193 * Process some data in the context case.
194 */
195
196METHODDEF(void)
197pre_process_context (j_compress_ptr cinfo,
198                     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
199                     JDIMENSION in_rows_avail,
200                     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
201                     JDIMENSION out_row_groups_avail)
202{
203  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
204  int numrows, ci;
205  int buf_height = cinfo->max_v_samp_factor * 3;
206  JDIMENSION inrows;
207
208  while (*out_row_group_ctr < out_row_groups_avail) {
209    if (*in_row_ctr < in_rows_avail) {
210      /* Do color conversion to fill the conversion buffer. */
211      inrows = in_rows_avail - *in_row_ctr;
212      numrows = prep->next_buf_stop - prep->next_buf_row;
213      numrows = (int) MIN((JDIMENSION) numrows, inrows);
214      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
215                                         prep->color_buf,
216                                         (JDIMENSION) prep->next_buf_row,
217                                         numrows);
218      /* Pad at top of image, if first time through */
219      if (prep->rows_to_go == cinfo->image_height) {
220        for (ci = 0; ci < cinfo->num_components; ci++) {
221          int row;
222          for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
223            jcopy_sample_rows(prep->color_buf[ci], 0,
224                              prep->color_buf[ci], -row,
225                              1, cinfo->image_width);
226          }
227        }
228      }
229      *in_row_ctr += numrows;
230      prep->next_buf_row += numrows;
231      prep->rows_to_go -= numrows;
232    } else {
233      /* Return for more data, unless we are at the bottom of the image. */
234      if (prep->rows_to_go != 0)
235        break;
236      /* When at bottom of image, pad to fill the conversion buffer. */
237      if (prep->next_buf_row < prep->next_buf_stop) {
238        for (ci = 0; ci < cinfo->num_components; ci++) {
239          expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
240                             prep->next_buf_row, prep->next_buf_stop);
241        }
242        prep->next_buf_row = prep->next_buf_stop;
243      }
244    }
245    /* If we've gotten enough data, downsample a row group. */
246    if (prep->next_buf_row == prep->next_buf_stop) {
247      (*cinfo->downsample->downsample) (cinfo,
248                                        prep->color_buf,
249                                        (JDIMENSION) prep->this_row_group,
250                                        output_buf, *out_row_group_ctr);
251      (*out_row_group_ctr)++;
252      /* Advance pointers with wraparound as necessary. */
253      prep->this_row_group += cinfo->max_v_samp_factor;
254      if (prep->this_row_group >= buf_height)
255        prep->this_row_group = 0;
256      if (prep->next_buf_row >= buf_height)
257        prep->next_buf_row = 0;
258      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
259    }
260  }
261}
262
263
264/*
265 * Create the wrapped-around downsampling input buffer needed for context mode.
266 */
267
268LOCAL(void)
269create_context_buffer (j_compress_ptr cinfo)
270{
271  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
272  int rgroup_height = cinfo->max_v_samp_factor;
273  int ci, i;
274  jpeg_component_info * compptr;
275  JSAMPARRAY true_buffer, fake_buffer;
276
277  /* Grab enough space for fake row pointers for all the components;
278   * we need five row groups' worth of pointers for each component.
279   */
280  fake_buffer = (JSAMPARRAY)
281    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
282                                (cinfo->num_components * 5 * rgroup_height) *
283                                SIZEOF(JSAMPROW));
284
285  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
286       ci++, compptr++) {
287    /* Allocate the actual buffer space (3 row groups) for this component.
288     * We make the buffer wide enough to allow the downsampler to edge-expand
289     * horizontally within the buffer, if it so chooses.
290     */
291    true_buffer = (*cinfo->mem->alloc_sarray)
292      ((j_common_ptr) cinfo, JPOOL_IMAGE,
293       (JDIMENSION) (((long) compptr->width_in_blocks *
294                      cinfo->min_DCT_h_scaled_size *
295                      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
296       (JDIMENSION) (3 * rgroup_height));
297    /* Copy true buffer row pointers into the middle of the fake row array */
298    MEMCOPY(fake_buffer + rgroup_height, true_buffer,
299            3 * rgroup_height * SIZEOF(JSAMPROW));
300    /* Fill in the above and below wraparound pointers */
301    for (i = 0; i < rgroup_height; i++) {
302      fake_buffer[i] = true_buffer[2 * rgroup_height + i];
303      fake_buffer[4 * rgroup_height + i] = true_buffer[i];
304    }
305    prep->color_buf[ci] = fake_buffer + rgroup_height;
306    fake_buffer += 5 * rgroup_height; /* point to space for next component */
307  }
308}
309
310#endif /* CONTEXT_ROWS_SUPPORTED */
311
312
313/*
314 * Initialize preprocessing controller.
315 */
316
317GLOBAL(void)
318jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
319{
320  my_prep_ptr prep;
321  int ci;
322  jpeg_component_info * compptr;
323
324  if (need_full_buffer)         /* safety check */
325    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
326
327  prep = (my_prep_ptr)
328    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
329                                SIZEOF(my_prep_controller));
330  cinfo->prep = (struct jpeg_c_prep_controller *) prep;
331  prep->pub.start_pass = start_pass_prep;
332
333  /* Allocate the color conversion buffer.
334   * We make the buffer wide enough to allow the downsampler to edge-expand
335   * horizontally within the buffer, if it so chooses.
336   */
337  if (cinfo->downsample->need_context_rows) {
338    /* Set up to provide context rows */
339#ifdef CONTEXT_ROWS_SUPPORTED
340    prep->pub.pre_process_data = pre_process_context;
341    create_context_buffer(cinfo);
342#else
343    ERREXIT(cinfo, JERR_NOT_COMPILED);
344#endif
345  } else {
346    /* No context, just make it tall enough for one row group */
347    prep->pub.pre_process_data = pre_process_data;
348    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
349         ci++, compptr++) {
350      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
351        ((j_common_ptr) cinfo, JPOOL_IMAGE,
352         (JDIMENSION) (((long) compptr->width_in_blocks *
353                        cinfo->min_DCT_h_scaled_size *
354                        cinfo->max_h_samp_factor) / compptr->h_samp_factor),
355         (JDIMENSION) cinfo->max_v_samp_factor);
356    }
357  }
358}
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