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
8 * For conditions of distribution and use, see the accompanying README.ijg
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.
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
22 #define JPEG_INTERNALS
27 /* Private buffer controller object */
30 struct jpeg_d_post_controller pub
; /* public fields */
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.
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 */
45 typedef my_post_controller
*my_post_ptr
;
48 /* Forward declarations */
49 METHODDEF(void) post_process_1pass(j_decompress_ptr cinfo
,
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
57 METHODDEF(void) post_process_prepass(j_decompress_ptr cinfo
,
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
);
64 METHODDEF(void) post_process_2pass(j_decompress_ptr cinfo
,
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
);
75 * Initialize for a processing pass.
79 start_pass_dpost(j_decompress_ptr cinfo
, J_BUF_MODE pass_mode
)
81 my_post_ptr post
= (my_post_ptr
)cinfo
->post
;
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.
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
);
98 /* For single-pass processing without color quantization,
99 * I have no work to do; just call the upsampler directly.
101 post
->pub
.post_process_data
= cinfo
->upsample
->upsample
;
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
;
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
;
117 #endif /* QUANT_2PASS_SUPPORTED */
119 ERREXIT(cinfo
, JERR_BAD_BUFFER_MODE
);
122 post
->starting_row
= post
->next_row
= 0;
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.
132 post_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
)
137 my_post_ptr post
= (my_post_ptr
)cinfo
->post
;
138 JDIMENSION num_rows
, max_rows
;
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
;
146 (*cinfo
->upsample
->upsample
) (cinfo
, input_buf
, in_row_group_ctr
,
147 in_row_groups_avail
, post
->buffer
, &num_rows
,
149 /* Quantize and emit data. */
150 (*cinfo
->cquantize
->color_quantize
) (cinfo
, post
->buffer
,
151 output_buf
+ *out_row_ctr
,
153 *out_row_ctr
+= num_rows
;
157 #ifdef QUANT_2PASS_SUPPORTED
160 * Process some data in the first pass of 2-pass quantization.
164 post_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
)
169 my_post_ptr post
= (my_post_ptr
)cinfo
->post
;
170 JDIMENSION old_next_row
, num_rows
;
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
);
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
);
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
;
194 /* Advance if we filled the strip. */
195 if (post
->next_row
>= post
->strip_height
) {
196 post
->starting_row
+= post
->strip_height
;
203 * Process some data in the second pass of 2-pass quantization.
207 post_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
)
212 my_post_ptr post
= (my_post_ptr
)cinfo
->post
;
213 JDIMENSION num_rows
, max_rows
;
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
);
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
)
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
)
232 /* Quantize and emit data. */
233 (*cinfo
->cquantize
->color_quantize
) (cinfo
, post
->buffer
+ post
->next_row
,
234 output_buf
+ *out_row_ctr
,
236 *out_row_ctr
+= num_rows
;
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
;
246 #endif /* QUANT_2PASS_SUPPORTED */
250 * Initialize postprocessing controller.
254 jinit_d_post_controller(j_decompress_ptr cinfo
, boolean need_full_buffer
)
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 */
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?)
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
),
284 ERREXIT(cinfo
, JERR_BAD_BUFFER_MODE
);
285 #endif /* QUANT_2PASS_SUPPORTED */
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
,