jcprepct.c
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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 
53 typedef 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  */
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
69 
71 
72 
73 /*
74  * Initialize for a processing pass.
75  */
76 
77 METHODDEF(void)
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 
105 LOCAL(void)
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 
127 METHODDEF(void)
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;
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++) {
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 
194 METHODDEF(void)
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 
266 LOCAL(void)
268 {
269  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
270  int rgroup_height = cinfo->max_v_samp_factor;
271  int ci, i;
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 
314 GLOBAL(void)
316 {
317  my_prep_ptr prep;
318  int ci;
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,
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 }
JSAMPLE FAR * JSAMPROW
Definition: jpeglib.h:66
JSAMPARRAY color_buf[MAX_COMPONENTS]
Definition: jcprepct.c:59
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:261
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)
Definition: jcprepct.c:195
#define MAX_COMPONENTS
Definition: jmorecfg.h:35
#define ERREXIT(cinfo, code)
Definition: jerror.h:205
#define MIN(a, b)
Returns the min value between a and b.
Definition: IceTypes.h:146
#define SIZEOF(object)
Definition: jinclude.h:80
boolean need_full_buffer
Definition: jpegint.h:338
png_uint_32 i
Definition: png.h:2735
jpeg_component_info * compptr
Definition: jdct.h:102
JDIMENSION width_in_blocks
Definition: jpeglib.h:139
#define JPOOL_IMAGE
Definition: jpeglib.h:749
my_prep_controller * my_prep_ptr
Definition: jcprepct.c:70
start_pass_prep(j_compress_ptr cinfo, J_BUF_MODE pass_mode)
Definition: jcprepct.c:78
#define MEMCOPY(dest, src, size)
Definition: jinclude.h:68
struct jpeg_c_prep_controller pub
Definition: jcprepct.c:54
#define LOCAL(type)
Definition: jmorecfg.h:186
png_bytepp row
Definition: png.h:1759
int JSAMPARRAY int int JDIMENSION num_cols
Definition: jpegint.h:373
JSAMPARRAY * JSAMPIMAGE
Definition: jpeglib.h:68
expand_bottom_edge(JSAMPARRAY image_data, JDIMENSION num_cols, int input_rows, int output_rows)
Definition: jcprepct.c:106
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)
Definition: jcprepct.c:128
JSAMPROW * JSAMPARRAY
Definition: jpeglib.h:67
typedef int
Definition: png.h:1113
#define GLOBAL(type)
Definition: jmorecfg.h:188
#define METHODDEF(type)
Definition: jmorecfg.h:184
J_BUF_MODE
Definition: jpegint.h:16
#define DCTSIZE
Definition: jpeglib.h:41
jpeg_component_info JCOEFPTR JSAMPARRAY output_buf
Definition: jdct.h:102
unsigned int JDIMENSION
Definition: jmorecfg.h:171
jcopy_sample_rows(JSAMPARRAY input_array, int source_row, JSAMPARRAY output_array, int dest_row, int num_rows, JDIMENSION num_cols)
Definition: jutils.c:111
create_context_buffer(j_compress_ptr cinfo)
Definition: jcprepct.c:267
jinit_c_prep_controller(j_compress_ptr cinfo, boolean need_full_buffer)
Definition: jcprepct.c:315
JDIMENSION rows_to_go
Definition: jcprepct.c:61


openhrp3
Author(s): AIST, General Robotix Inc., Nakamura Lab of Dept. of Mechano Informatics at University of Tokyo
autogenerated on Sat Apr 13 2019 02:14:23