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