source: trunk/libjpeg/jcprepct.c @ 15

Last change on this file since 15 was 15, checked in by Eugene Romanenko, 15 years ago

needed libs update

File size: 12.1 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        expand_bottom_edge(output_buf[ci],
177                           compptr->width_in_blocks * DCTSIZE,
178                           (int) (*out_row_group_ctr * compptr->v_samp_factor),
179                           (int) (out_row_groups_avail * compptr->v_samp_factor));
180      }
181      *out_row_group_ctr = out_row_groups_avail;
182      break;                    /* can exit outer loop without test */
183    }
184  }
185}
186
187
188#ifdef CONTEXT_ROWS_SUPPORTED
189
190/*
191 * Process some data in the context case.
192 */
193
194METHODDEF(void)
195pre_process_context (j_compress_ptr cinfo,
196                     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
197                     JDIMENSION in_rows_avail,
198                     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
199                     JDIMENSION out_row_groups_avail)
200{
201  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
202  int numrows, ci;
203  int buf_height = cinfo->max_v_samp_factor * 3;
204  JDIMENSION inrows;
205
206  while (*out_row_group_ctr < out_row_groups_avail) {
207    if (*in_row_ctr < in_rows_avail) {
208      /* Do color conversion to fill the conversion buffer. */
209      inrows = in_rows_avail - *in_row_ctr;
210      numrows = prep->next_buf_stop - prep->next_buf_row;
211      numrows = (int) MIN((JDIMENSION) numrows, inrows);
212      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
213                                         prep->color_buf,
214                                         (JDIMENSION) prep->next_buf_row,
215                                         numrows);
216      /* Pad at top of image, if first time through */
217      if (prep->rows_to_go == cinfo->image_height) {
218        for (ci = 0; ci < cinfo->num_components; ci++) {
219          int row;
220          for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
221            jcopy_sample_rows(prep->color_buf[ci], 0,
222                              prep->color_buf[ci], -row,
223                              1, cinfo->image_width);
224          }
225        }
226      }
227      *in_row_ctr += numrows;
228      prep->next_buf_row += numrows;
229      prep->rows_to_go -= numrows;
230    } else {
231      /* Return for more data, unless we are at the bottom of the image. */
232      if (prep->rows_to_go != 0)
233        break;
234      /* When at bottom of image, pad to fill the conversion buffer. */
235      if (prep->next_buf_row < prep->next_buf_stop) {
236        for (ci = 0; ci < cinfo->num_components; ci++) {
237          expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
238                             prep->next_buf_row, prep->next_buf_stop);
239        }
240        prep->next_buf_row = prep->next_buf_stop;
241      }
242    }
243    /* If we've gotten enough data, downsample a row group. */
244    if (prep->next_buf_row == prep->next_buf_stop) {
245      (*cinfo->downsample->downsample) (cinfo,
246                                        prep->color_buf,
247                                        (JDIMENSION) prep->this_row_group,
248                                        output_buf, *out_row_group_ctr);
249      (*out_row_group_ctr)++;
250      /* Advance pointers with wraparound as necessary. */
251      prep->this_row_group += cinfo->max_v_samp_factor;
252      if (prep->this_row_group >= buf_height)
253        prep->this_row_group = 0;
254      if (prep->next_buf_row >= buf_height)
255        prep->next_buf_row = 0;
256      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
257    }
258  }
259}
260
261
262/*
263 * Create the wrapped-around downsampling input buffer needed for context mode.
264 */
265
266LOCAL(void)
267create_context_buffer (j_compress_ptr cinfo)
268{
269  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
270  int rgroup_height = cinfo->max_v_samp_factor;
271  int ci, i;
272  jpeg_component_info * compptr;
273  JSAMPARRAY true_buffer, fake_buffer;
274
275  /* Grab enough space for fake row pointers for all the components;
276   * we need five row groups' worth of pointers for each component.
277   */
278  fake_buffer = (JSAMPARRAY)
279    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
280                                (cinfo->num_components * 5 * rgroup_height) *
281                                SIZEOF(JSAMPROW));
282
283  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
284       ci++, compptr++) {
285    /* Allocate the actual buffer space (3 row groups) for this component.
286     * We make the buffer wide enough to allow the downsampler to edge-expand
287     * horizontally within the buffer, if it so chooses.
288     */
289    true_buffer = (*cinfo->mem->alloc_sarray)
290      ((j_common_ptr) cinfo, JPOOL_IMAGE,
291       (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
292                      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
293       (JDIMENSION) (3 * rgroup_height));
294    /* Copy true buffer row pointers into the middle of the fake row array */
295    MEMCOPY(fake_buffer + rgroup_height, true_buffer,
296            3 * rgroup_height * SIZEOF(JSAMPROW));
297    /* Fill in the above and below wraparound pointers */
298    for (i = 0; i < rgroup_height; i++) {
299      fake_buffer[i] = true_buffer[2 * rgroup_height + i];
300      fake_buffer[4 * rgroup_height + i] = true_buffer[i];
301    }
302    prep->color_buf[ci] = fake_buffer + rgroup_height;
303    fake_buffer += 5 * rgroup_height; /* point to space for next component */
304  }
305}
306
307#endif /* CONTEXT_ROWS_SUPPORTED */
308
309
310/*
311 * Initialize preprocessing controller.
312 */
313
314GLOBAL(void)
315jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
316{
317  my_prep_ptr prep;
318  int ci;
319  jpeg_component_info * compptr;
320
321  if (need_full_buffer)         /* safety check */
322    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
323
324  prep = (my_prep_ptr)
325    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
326                                SIZEOF(my_prep_controller));
327  cinfo->prep = (struct jpeg_c_prep_controller *) prep;
328  prep->pub.start_pass = start_pass_prep;
329
330  /* Allocate the color conversion buffer.
331   * We make the buffer wide enough to allow the downsampler to edge-expand
332   * horizontally within the buffer, if it so chooses.
333   */
334  if (cinfo->downsample->need_context_rows) {
335    /* Set up to provide context rows */
336#ifdef CONTEXT_ROWS_SUPPORTED
337    prep->pub.pre_process_data = pre_process_context;
338    create_context_buffer(cinfo);
339#else
340    ERREXIT(cinfo, JERR_NOT_COMPILED);
341#endif
342  } else {
343    /* No context, just make it tall enough for one row group */
344    prep->pub.pre_process_data = pre_process_data;
345    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
346         ci++, compptr++) {
347      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
348        ((j_common_ptr) cinfo, JPOOL_IMAGE,
349         (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
350                        cinfo->max_h_samp_factor) / compptr->h_samp_factor),
351         (JDIMENSION) cinfo->max_v_samp_factor);
352    }
353  }
354}
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