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
50        (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
51         JDIMENSION *in_row_group_ctr, JDIMENSION in_row_groups_avail,
52         JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
53         JDIMENSION out_rows_avail);
54#ifdef QUANT_2PASS_SUPPORTED
55METHODDEF(void) post_process_prepass
56        (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
57         JDIMENSION *in_row_group_ctr, JDIMENSION in_row_groups_avail,
58         JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
59         JDIMENSION out_rows_avail);
60METHODDEF(void) post_process_2pass
61        (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
62         JDIMENSION *in_row_group_ctr, 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