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JPG support.
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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
26 typedef 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
42 typedef my_post_controller * my_post_ptr;
43
44
45 /* Forward declarations */
46 METHODDEF(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
53 METHODDEF(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));
59 METHODDEF(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
72 METHODDEF(void)
73 start_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
125 METHODDEF(void)
126 post_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
157 METHODDEF(void)
158 post_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
201 METHODDEF(void)
202 post_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
249 GLOBAL(void)
250 jinit_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 }