1/*
2 * jdpostct.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 decompression postprocessing controller.
9 * This controller manages the upsampling, color conversion, and color
10 * quantization/reduction steps; specifically, it controls the buffering
11 * between upsample/color conversion and color quantization/reduction.
12 *
13 * If no color quantization/reduction is required, then this module has no
14 * work to do, and it just hands off to the upsample/color conversion code.
15 * An integrated upsample/convert/quantize process would replace this module
16 * entirely.
17 */
18
19#define JPEG_INTERNALS
20#include "jinclude.h"
21#include "jpeglib.h"
22
23
24/* Private buffer controller object */
25
26typedef struct {
27 struct jpeg_d_post_controller pub; /* public fields */
28
29 /* Color quantization source buffer: this holds output data from
30 * the upsample/color conversion step to be passed to the quantizer.
31 * For two-pass color quantization, we need a full-image buffer;
32 * for one-pass operation, a strip buffer is sufficient.
33 */
34 jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
35 JSAMPARRAY buffer; /* strip buffer, or current strip of virtual */
36 JDIMENSION strip_height; /* buffer size in rows */
37 /* for two-pass mode only: */
38 JDIMENSION starting_row; /* row # of first row in current strip */
39 JDIMENSION next_row; /* index of next row to fill/empty in strip */
40} my_post_controller;
41
42typedef my_post_controller * my_post_ptr;
43
44
45/* Forward declarations */
46METHODDEF(void) post_process_1pass
47 JPP((j_decompress_ptr cinfo,
48 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
49 JDIMENSION in_row_groups_avail,
50 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
51 JDIMENSION out_rows_avail));
52#ifdef QUANT_2PASS_SUPPORTED
53METHODDEF(void) post_process_prepass
54 JPP((j_decompress_ptr cinfo,
55 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
56 JDIMENSION in_row_groups_avail,
57 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
58 JDIMENSION out_rows_avail));
59METHODDEF(void) post_process_2pass
60 JPP((j_decompress_ptr cinfo,
61 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
62 JDIMENSION in_row_groups_avail,
63 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
64 JDIMENSION out_rows_avail));
65#endif
66
67
68/*
69 * Initialize for a processing pass.
70 */
71
72METHODDEF(void)
73start_pass_dpost (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
74{
75 my_post_ptr post = (my_post_ptr) cinfo->post;
76
77 switch (pass_mode) {
78 case JBUF_PASS_THRU:
79 if (cinfo->quantize_colors) {
80 /* Single-pass processing with color quantization. */
81 post->pub.post_process_data = post_process_1pass;
82 /* We could be doing buffered-image output before starting a 2-pass
83 * color quantization; in that case, jinit_d_post_controller did not
84 * allocate a strip buffer. Use the virtual-array buffer as workspace.
85 */
86 if (post->buffer == NULL) {
87 post->buffer = (*cinfo->mem->access_virt_sarray)
88 ((j_common_ptr) cinfo, post->whole_image,
89 (JDIMENSION) 0, post->strip_height, TRUE);
90 }
91 } else {
92 /* For single-pass processing without color quantization,
93 * I have no work to do; just call the upsampler directly.
94 */
95 post->pub.post_process_data = cinfo->upsample->upsample;
96 }
97 break;
98#ifdef QUANT_2PASS_SUPPORTED
99 case JBUF_SAVE_AND_PASS:
100 /* First pass of 2-pass quantization */
101 if (post->whole_image == NULL)
102 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
103 post->pub.post_process_data = post_process_prepass;
104 break;
105 case JBUF_CRANK_DEST:
106 /* Second 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_2pass;
110 break;
111#endif /* QUANT_2PASS_SUPPORTED */
112 default:
113 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
114 break;
115 }
116 post->starting_row = post->next_row = 0;
117}
118
119
120/*
121 * Process some data in the one-pass (strip buffer) case.
122 * This is used for color precision reduction as well as one-pass quantization.
123 */
124
125METHODDEF(void)
126post_process_1pass (j_decompress_ptr cinfo,
127 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
128 JDIMENSION in_row_groups_avail,
129 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
130 JDIMENSION out_rows_avail)
131{
132 my_post_ptr post = (my_post_ptr) cinfo->post;
133 JDIMENSION num_rows, max_rows;
134
135 /* Fill the buffer, but not more than what we can dump out in one go. */
136 /* Note we rely on the upsampler to detect bottom of image. */
137 max_rows = out_rows_avail - *out_row_ctr;
138 if (max_rows > post->strip_height)
139 max_rows = post->strip_height;
140 num_rows = 0;
141 (*cinfo->upsample->upsample) (cinfo,
142 input_buf, in_row_group_ctr, in_row_groups_avail,
143 post->buffer, &num_rows, max_rows);
144 /* Quantize and emit data. */
145 (*cinfo->cquantize->color_quantize) (cinfo,
146 post->buffer, output_buf + *out_row_ctr, (int) num_rows);
147 *out_row_ctr += num_rows;
148}
149
150
151#ifdef QUANT_2PASS_SUPPORTED
152
153/*
154 * Process some data in the first pass of 2-pass quantization.
155 */
156
157METHODDEF(void)
158post_process_prepass (j_decompress_ptr cinfo,
159 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
160 JDIMENSION in_row_groups_avail,
161 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
162 JDIMENSION out_rows_avail)
163{
164 my_post_ptr post = (my_post_ptr) cinfo->post;
165 JDIMENSION old_next_row, num_rows;
166
167 /* Reposition virtual buffer if at start of strip. */
168 if (post->next_row == 0) {
169 post->buffer = (*cinfo->mem->access_virt_sarray)
170 ((j_common_ptr) cinfo, post->whole_image,
171 post->starting_row, post->strip_height, TRUE);
172 }
173
174 /* Upsample some data (up to a strip height's worth). */
175 old_next_row = post->next_row;
176 (*cinfo->upsample->upsample) (cinfo,
177 input_buf, in_row_group_ctr, in_row_groups_avail,
178 post->buffer, &post->next_row, post->strip_height);
179
180 /* Allow quantizer to scan new data. No data is emitted, */
181 /* but we advance out_row_ctr so outer loop can tell when we're done. */
182 if (post->next_row > old_next_row) {
183 num_rows = post->next_row - old_next_row;
184 (*cinfo->cquantize->color_quantize) (cinfo, post->buffer + old_next_row,
185 (JSAMPARRAY) NULL, (int) num_rows);
186 *out_row_ctr += num_rows;
187 }
188
189 /* Advance if we filled the strip. */
190 if (post->next_row >= post->strip_height) {
191 post->starting_row += post->strip_height;
192 post->next_row = 0;
193 }
194}
195
196
197/*
198 * Process some data in the second pass of 2-pass quantization.
199 */
200
201METHODDEF(void)
202post_process_2pass (j_decompress_ptr cinfo,
203 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
204 JDIMENSION in_row_groups_avail,
205 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
206 JDIMENSION out_rows_avail)
207{
208 my_post_ptr post = (my_post_ptr) cinfo->post;
209 JDIMENSION num_rows, max_rows;
210
211 /* Reposition virtual buffer if at start of strip. */
212 if (post->next_row == 0) {
213 post->buffer = (*cinfo->mem->access_virt_sarray)
214 ((j_common_ptr) cinfo, post->whole_image,
215 post->starting_row, post->strip_height, FALSE);
216 }
217
218 /* Determine number of rows to emit. */
219 num_rows = post->strip_height - post->next_row; /* available in strip */
220 max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
221 if (num_rows > max_rows)
222 num_rows = max_rows;
223 /* We have to check bottom of image here, can't depend on upsampler. */
224 max_rows = cinfo->output_height - post->starting_row;
225 if (num_rows > max_rows)
226 num_rows = max_rows;
227
228 /* Quantize and emit data. */
229 (*cinfo->cquantize->color_quantize) (cinfo,
230 post->buffer + post->next_row, output_buf + *out_row_ctr,
231 (int) num_rows);
232 *out_row_ctr += num_rows;
233
234 /* Advance if we filled the strip. */
235 post->next_row += num_rows;
236 if (post->next_row >= post->strip_height) {
237 post->starting_row += post->strip_height;
238 post->next_row = 0;
239 }
240}
241
242#endif /* QUANT_2PASS_SUPPORTED */
243
244
245/*
246 * Initialize postprocessing controller.
247 */
248
249GLOBAL(void)
250jinit_d_post_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
251{
252 my_post_ptr post;
253
254 post = (my_post_ptr)
255 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
256 SIZEOF(my_post_controller));
257 cinfo->post = (struct jpeg_d_post_controller *) post;
258 post->pub.start_pass = start_pass_dpost;
259 post->whole_image = NULL; /* flag for no virtual arrays */
260 post->buffer = NULL; /* flag for no strip buffer */
261
262 /* Create the quantization buffer, if needed */
263 if (cinfo->quantize_colors) {
264 /* The buffer strip height is max_v_samp_factor, which is typically
265 * an efficient number of rows for upsampling to return.
266 * (In the presence of output rescaling, we might want to be smarter?)
267 */
268 post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
269 if (need_full_buffer) {
270 /* Two-pass color quantization: need full-image storage. */
271 /* We round up the number of rows to a multiple of the strip height. */
272#ifdef QUANT_2PASS_SUPPORTED
273 post->whole_image = (*cinfo->mem->request_virt_sarray)
274 ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
275 cinfo->output_width * cinfo->out_color_components,
276 (JDIMENSION) jround_up((long) cinfo->output_height,
277 (long) post->strip_height),
278 post->strip_height);
279#else
280 ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
281#endif /* QUANT_2PASS_SUPPORTED */
282 } else {
283 /* One-pass color quantization: just make a strip buffer. */
284 post->buffer = (*cinfo->mem->alloc_sarray)
285 ((j_common_ptr) cinfo, JPOOL_IMAGE,
286 cinfo->output_width * cinfo->out_color_components,
287 post->strip_height);
288 }
289 }
290}
291