1/*
2 * jdpostct.c
3 *
4 * This file was 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 decompression postprocessing controller.
12 * This controller manages the upsampling, color conversion, and color
13 * quantization/reduction steps; specifically, it controls the buffering
14 * between upsample/color conversion and color quantization/reduction.
15 *
16 * If no color quantization/reduction is required, then this module has no
17 * work to do, and it just hands off to the upsample/color conversion code.
18 * An integrated upsample/convert/quantize process would replace this module
19 * entirely.
20 */
21
22#define JPEG_INTERNALS
23#include "jinclude.h"
24#include "jpeglib.h"
25
26
27/* Private buffer controller object */
28
29typedef struct {
30 struct jpeg_d_post_controller pub; /* public fields */
31
32 /* Color quantization source buffer: this holds output data from
33 * the upsample/color conversion step to be passed to the quantizer.
34 * For two-pass color quantization, we need a full-image buffer;
35 * for one-pass operation, a strip buffer is sufficient.
36 */
37 jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
38 JSAMPARRAY buffer; /* strip buffer, or current strip of virtual */
39 JDIMENSION strip_height; /* buffer size in rows */
40 /* for two-pass mode only: */
41 JDIMENSION starting_row; /* row # of first row in current strip */
42 JDIMENSION next_row; /* index of next row to fill/empty in strip */
43} my_post_controller;
44
45typedef my_post_controller *my_post_ptr;
46
47
48/* Forward declarations */
49METHODDEF(void) post_process_1pass(j_decompress_ptr cinfo,
50 JSAMPIMAGE input_buf,
51 JDIMENSION *in_row_group_ctr,
52 JDIMENSION in_row_groups_avail,
53 JSAMPARRAY output_buf,
54 JDIMENSION *out_row_ctr,
55 JDIMENSION out_rows_avail);
56#ifdef QUANT_2PASS_SUPPORTED
57METHODDEF(void) post_process_prepass(j_decompress_ptr cinfo,
58 JSAMPIMAGE input_buf,
59 JDIMENSION *in_row_group_ctr,
60 JDIMENSION in_row_groups_avail,
61 JSAMPARRAY output_buf,
62 JDIMENSION *out_row_ctr,
63 JDIMENSION out_rows_avail);
64METHODDEF(void) post_process_2pass(j_decompress_ptr cinfo,
65 JSAMPIMAGE input_buf,
66 JDIMENSION *in_row_group_ctr,
67 JDIMENSION in_row_groups_avail,
68 JSAMPARRAY output_buf,
69 JDIMENSION *out_row_ctr,
70 JDIMENSION out_rows_avail);
71#endif
72
73
74/*
75 * Initialize for a processing pass.
76 */
77
78METHODDEF(void)
79start_pass_dpost(j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
80{
81 my_post_ptr post = (my_post_ptr)cinfo->post;
82
83 switch (pass_mode) {
84 case JBUF_PASS_THRU:
85 if (cinfo->quantize_colors) {
86 /* Single-pass processing with color quantization. */
87 post->pub.post_process_data = post_process_1pass;
88 /* We could be doing buffered-image output before starting a 2-pass
89 * color quantization; in that case, jinit_d_post_controller did not
90 * allocate a strip buffer. Use the virtual-array buffer as workspace.
91 */
92 if (post->buffer == NULL) {
93 post->buffer = (*cinfo->mem->access_virt_sarray)
94 ((j_common_ptr)cinfo, post->whole_image,
95 (JDIMENSION)0, post->strip_height, TRUE);
96 }
97 } else {
98 /* For single-pass processing without color quantization,
99 * I have no work to do; just call the upsampler directly.
100 */
101 post->pub.post_process_data = cinfo->upsample->upsample;
102 }
103 break;
104#ifdef QUANT_2PASS_SUPPORTED
105 case JBUF_SAVE_AND_PASS:
106 /* First pass of 2-pass quantization */
107 if (post->whole_image == NULL)
108 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
109 post->pub.post_process_data = post_process_prepass;
110 break;
111 case JBUF_CRANK_DEST:
112 /* Second pass of 2-pass quantization */
113 if (post->whole_image == NULL)
114 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
115 post->pub.post_process_data = post_process_2pass;
116 break;
117#endif /* QUANT_2PASS_SUPPORTED */
118 default:
119 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
120 break;
121 }
122 post->starting_row = post->next_row = 0;
123}
124
125
126/*
127 * Process some data in the one-pass (strip buffer) case.
128 * This is used for color precision reduction as well as one-pass quantization.
129 */
130
131METHODDEF(void)
132post_process_1pass(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
133 JDIMENSION *in_row_group_ctr,
134 JDIMENSION in_row_groups_avail, JSAMPARRAY output_buf,
135 JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
136{
137 my_post_ptr post = (my_post_ptr)cinfo->post;
138 JDIMENSION num_rows, max_rows;
139
140 /* Fill the buffer, but not more than what we can dump out in one go. */
141 /* Note we rely on the upsampler to detect bottom of image. */
142 max_rows = out_rows_avail - *out_row_ctr;
143 if (max_rows > post->strip_height)
144 max_rows = post->strip_height;
145 num_rows = 0;
146 (*cinfo->upsample->upsample) (cinfo, input_buf, in_row_group_ctr,
147 in_row_groups_avail, post->buffer, &num_rows,
148 max_rows);
149 /* Quantize and emit data. */
150 (*cinfo->cquantize->color_quantize) (cinfo, post->buffer,
151 output_buf + *out_row_ctr,
152 (int)num_rows);
153 *out_row_ctr += num_rows;
154}
155
156
157#ifdef QUANT_2PASS_SUPPORTED
158
159/*
160 * Process some data in the first pass of 2-pass quantization.
161 */
162
163METHODDEF(void)
164post_process_prepass(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
165 JDIMENSION *in_row_group_ctr,
166 JDIMENSION in_row_groups_avail, JSAMPARRAY output_buf,
167 JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
168{
169 my_post_ptr post = (my_post_ptr)cinfo->post;
170 JDIMENSION old_next_row, num_rows;
171
172 /* Reposition virtual buffer if at start of strip. */
173 if (post->next_row == 0) {
174 post->buffer = (*cinfo->mem->access_virt_sarray)
175 ((j_common_ptr)cinfo, post->whole_image,
176 post->starting_row, post->strip_height, TRUE);
177 }
178
179 /* Upsample some data (up to a strip height's worth). */
180 old_next_row = post->next_row;
181 (*cinfo->upsample->upsample) (cinfo, input_buf, in_row_group_ctr,
182 in_row_groups_avail, post->buffer,
183 &post->next_row, post->strip_height);
184
185 /* Allow quantizer to scan new data. No data is emitted, */
186 /* but we advance out_row_ctr so outer loop can tell when we're done. */
187 if (post->next_row > old_next_row) {
188 num_rows = post->next_row - old_next_row;
189 (*cinfo->cquantize->color_quantize) (cinfo, post->buffer + old_next_row,
190 (JSAMPARRAY)NULL, (int)num_rows);
191 *out_row_ctr += num_rows;
192 }
193
194 /* Advance if we filled the strip. */
195 if (post->next_row >= post->strip_height) {
196 post->starting_row += post->strip_height;
197 post->next_row = 0;
198 }
199}
200
201
202/*
203 * Process some data in the second pass of 2-pass quantization.
204 */
205
206METHODDEF(void)
207post_process_2pass(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
208 JDIMENSION *in_row_group_ctr,
209 JDIMENSION in_row_groups_avail, JSAMPARRAY output_buf,
210 JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
211{
212 my_post_ptr post = (my_post_ptr)cinfo->post;
213 JDIMENSION num_rows, max_rows;
214
215 /* Reposition virtual buffer if at start of strip. */
216 if (post->next_row == 0) {
217 post->buffer = (*cinfo->mem->access_virt_sarray)
218 ((j_common_ptr)cinfo, post->whole_image,
219 post->starting_row, post->strip_height, FALSE);
220 }
221
222 /* Determine number of rows to emit. */
223 num_rows = post->strip_height - post->next_row; /* available in strip */
224 max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
225 if (num_rows > max_rows)
226 num_rows = max_rows;
227 /* We have to check bottom of image here, can't depend on upsampler. */
228 max_rows = cinfo->output_height - post->starting_row;
229 if (num_rows > max_rows)
230 num_rows = max_rows;
231
232 /* Quantize and emit data. */
233 (*cinfo->cquantize->color_quantize) (cinfo, post->buffer + post->next_row,
234 output_buf + *out_row_ctr,
235 (int)num_rows);
236 *out_row_ctr += num_rows;
237
238 /* Advance if we filled the strip. */
239 post->next_row += num_rows;
240 if (post->next_row >= post->strip_height) {
241 post->starting_row += post->strip_height;
242 post->next_row = 0;
243 }
244}
245
246#endif /* QUANT_2PASS_SUPPORTED */
247
248
249/*
250 * Initialize postprocessing controller.
251 */
252
253GLOBAL(void)
254jinit_d_post_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
255{
256 my_post_ptr post;
257
258 post = (my_post_ptr)
259 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
260 sizeof(my_post_controller));
261 cinfo->post = (struct jpeg_d_post_controller *)post;
262 post->pub.start_pass = start_pass_dpost;
263 post->whole_image = NULL; /* flag for no virtual arrays */
264 post->buffer = NULL; /* flag for no strip buffer */
265
266 /* Create the quantization buffer, if needed */
267 if (cinfo->quantize_colors) {
268 /* The buffer strip height is max_v_samp_factor, which is typically
269 * an efficient number of rows for upsampling to return.
270 * (In the presence of output rescaling, we might want to be smarter?)
271 */
272 post->strip_height = (JDIMENSION)cinfo->max_v_samp_factor;
273 if (need_full_buffer) {
274 /* Two-pass color quantization: need full-image storage. */
275 /* We round up the number of rows to a multiple of the strip height. */
276#ifdef QUANT_2PASS_SUPPORTED
277 post->whole_image = (*cinfo->mem->request_virt_sarray)
278 ((j_common_ptr)cinfo, JPOOL_IMAGE, FALSE,
279 cinfo->output_width * cinfo->out_color_components,
280 (JDIMENSION)jround_up((long)cinfo->output_height,
281 (long)post->strip_height),
282 post->strip_height);
283#else
284 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
285#endif /* QUANT_2PASS_SUPPORTED */
286 } else {
287 /* One-pass color quantization: just make a strip buffer. */
288 post->buffer = (*cinfo->mem->alloc_sarray)
289 ((j_common_ptr)cinfo, JPOOL_IMAGE,
290 cinfo->output_width * cinfo->out_color_components,
291 post->strip_height);
292 }
293 }
294}
295