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