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 : */
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 :
70 : typedef my_prep_controller * my_prep_ptr;
71 :
72 :
73 : /*
74 : * Initialize for a processing pass.
75 : */
76 :
77 : METHODDEF(void)
78 3 : start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
79 : {
80 3 : my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
81 :
82 3 : if (pass_mode != JBUF_PASS_THRU)
83 0 : ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
84 :
85 : /* Initialize total-height counter for detecting bottom of image */
86 3 : prep->rows_to_go = cinfo->image_height;
87 : /* Mark the conversion buffer empty */
88 3 : 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 3 : prep->this_row_group = 0;
94 : /* Set next_buf_stop to stop after two row groups have been read in. */
95 3 : prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
96 : #endif
97 3 : }
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)
106 0 : expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
107 : int input_rows, int output_rows)
108 : {
109 : register int row;
110 :
111 0 : for (row = input_rows; row < output_rows; row++) {
112 0 : jcopy_sample_rows(image_data, input_rows-1, image_data, row,
113 : 1, num_cols);
114 : }
115 0 : }
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)
128 159 : pre_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 : {
134 159 : my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
135 : int numrows, ci;
136 : JDIMENSION inrows;
137 : jpeg_component_info * compptr;
138 :
139 606 : while (*in_row_ctr < in_rows_avail &&
140 144 : *out_row_group_ctr < out_row_groups_avail) {
141 : /* Do color conversion to fill the conversion buffer. */
142 144 : inrows = in_rows_avail - *in_row_ctr;
143 144 : numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
144 144 : numrows = (int) MIN((JDIMENSION) numrows, inrows);
145 288 : (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
146 : prep->color_buf,
147 144 : (JDIMENSION) prep->next_buf_row,
148 : numrows);
149 144 : *in_row_ctr += numrows;
150 144 : prep->next_buf_row += numrows;
151 144 : prep->rows_to_go -= numrows;
152 : /* If at bottom of image, pad to fill the conversion buffer. */
153 147 : if (prep->rows_to_go == 0 &&
154 3 : prep->next_buf_row < cinfo->max_v_samp_factor) {
155 0 : for (ci = 0; ci < cinfo->num_components; ci++) {
156 0 : expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
157 : prep->next_buf_row, cinfo->max_v_samp_factor);
158 : }
159 0 : prep->next_buf_row = cinfo->max_v_samp_factor;
160 : }
161 : /* If we've filled the conversion buffer, empty it. */
162 144 : if (prep->next_buf_row == cinfo->max_v_samp_factor) {
163 144 : (*cinfo->downsample->downsample) (cinfo,
164 : prep->color_buf, (JDIMENSION) 0,
165 : output_buf, *out_row_group_ctr);
166 144 : prep->next_buf_row = 0;
167 144 : (*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 : */
172 147 : if (prep->rows_to_go == 0 &&
173 3 : *out_row_group_ctr < out_row_groups_avail) {
174 0 : for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
175 0 : ci++, compptr++) {
176 0 : expand_bottom_edge(output_buf[ci],
177 0 : compptr->width_in_blocks * DCTSIZE,
178 0 : (int) (*out_row_group_ctr * compptr->v_samp_factor),
179 0 : (int) (out_row_groups_avail * compptr->v_samp_factor));
180 : }
181 0 : *out_row_group_ctr = out_row_groups_avail;
182 0 : break; /* can exit outer loop without test */
183 : }
184 : }
185 159 : }
186 :
187 :
188 : #ifdef CONTEXT_ROWS_SUPPORTED
189 :
190 : /*
191 : * Process some data in the context case.
192 : */
193 :
194 : METHODDEF(void)
195 0 : pre_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 0 : my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
202 : int numrows, ci;
203 0 : int buf_height = cinfo->max_v_samp_factor * 3;
204 : JDIMENSION inrows;
205 :
206 0 : while (*out_row_group_ctr < out_row_groups_avail) {
207 0 : if (*in_row_ctr < in_rows_avail) {
208 : /* Do color conversion to fill the conversion buffer. */
209 0 : inrows = in_rows_avail - *in_row_ctr;
210 0 : numrows = prep->next_buf_stop - prep->next_buf_row;
211 0 : numrows = (int) MIN((JDIMENSION) numrows, inrows);
212 0 : (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
213 : prep->color_buf,
214 0 : (JDIMENSION) prep->next_buf_row,
215 : numrows);
216 : /* Pad at top of image, if first time through */
217 0 : if (prep->rows_to_go == cinfo->image_height) {
218 0 : for (ci = 0; ci < cinfo->num_components; ci++) {
219 : int row;
220 0 : for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
221 0 : jcopy_sample_rows(prep->color_buf[ci], 0,
222 : prep->color_buf[ci], -row,
223 : 1, cinfo->image_width);
224 : }
225 : }
226 : }
227 0 : *in_row_ctr += numrows;
228 0 : prep->next_buf_row += numrows;
229 0 : prep->rows_to_go -= numrows;
230 : } else {
231 : /* Return for more data, unless we are at the bottom of the image. */
232 0 : if (prep->rows_to_go != 0)
233 0 : break;
234 : /* When at bottom of image, pad to fill the conversion buffer. */
235 0 : if (prep->next_buf_row < prep->next_buf_stop) {
236 0 : for (ci = 0; ci < cinfo->num_components; ci++) {
237 0 : expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
238 : prep->next_buf_row, prep->next_buf_stop);
239 : }
240 0 : prep->next_buf_row = prep->next_buf_stop;
241 : }
242 : }
243 : /* If we've gotten enough data, downsample a row group. */
244 0 : if (prep->next_buf_row == prep->next_buf_stop) {
245 0 : (*cinfo->downsample->downsample) (cinfo,
246 : prep->color_buf,
247 0 : (JDIMENSION) prep->this_row_group,
248 : output_buf, *out_row_group_ctr);
249 0 : (*out_row_group_ctr)++;
250 : /* Advance pointers with wraparound as necessary. */
251 0 : prep->this_row_group += cinfo->max_v_samp_factor;
252 0 : if (prep->this_row_group >= buf_height)
253 0 : prep->this_row_group = 0;
254 0 : if (prep->next_buf_row >= buf_height)
255 0 : prep->next_buf_row = 0;
256 0 : prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
257 : }
258 : }
259 0 : }
260 :
261 :
262 : /*
263 : * Create the wrapped-around downsampling input buffer needed for context mode.
264 : */
265 :
266 : LOCAL(void)
267 0 : create_context_buffer (j_compress_ptr cinfo)
268 : {
269 0 : my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
270 0 : 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 0 : fake_buffer = (JSAMPARRAY)
279 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
280 0 : (cinfo->num_components * 5 * rgroup_height) *
281 : SIZEOF(JSAMPROW));
282 :
283 0 : for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
284 0 : 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 0 : true_buffer = (*cinfo->mem->alloc_sarray)
290 0 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
291 0 : (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
292 0 : cinfo->max_h_samp_factor) / compptr->h_samp_factor),
293 0 : (JDIMENSION) (3 * rgroup_height));
294 : /* Copy true buffer row pointers into the middle of the fake row array */
295 0 : MEMCOPY(fake_buffer + rgroup_height, true_buffer,
296 : 3 * rgroup_height * SIZEOF(JSAMPROW));
297 : /* Fill in the above and below wraparound pointers */
298 0 : for (i = 0; i < rgroup_height; i++) {
299 0 : fake_buffer[i] = true_buffer[2 * rgroup_height + i];
300 0 : fake_buffer[4 * rgroup_height + i] = true_buffer[i];
301 : }
302 0 : prep->color_buf[ci] = fake_buffer + rgroup_height;
303 0 : fake_buffer += 5 * rgroup_height; /* point to space for next component */
304 : }
305 0 : }
306 :
307 : #endif /* CONTEXT_ROWS_SUPPORTED */
308 :
309 :
310 : /*
311 : * Initialize preprocessing controller.
312 : */
313 :
314 : GLOBAL(void)
315 3 : jinit_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 3 : if (need_full_buffer) /* safety check */
322 0 : ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
323 :
324 3 : prep = (my_prep_ptr)
325 3 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
326 : SIZEOF(my_prep_controller));
327 3 : cinfo->prep = (struct jpeg_c_prep_controller *) prep;
328 3 : 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 3 : if (cinfo->downsample->need_context_rows) {
335 : /* Set up to provide context rows */
336 : #ifdef CONTEXT_ROWS_SUPPORTED
337 0 : prep->pub.pre_process_data = pre_process_context;
338 0 : 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 3 : prep->pub.pre_process_data = pre_process_data;
345 15 : for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
346 9 : ci++, compptr++) {
347 18 : prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
348 27 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
349 18 : (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
350 18 : cinfo->max_h_samp_factor) / compptr->h_samp_factor),
351 9 : (JDIMENSION) cinfo->max_v_samp_factor);
352 : }
353 : }
354 3 : }
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