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jdmerge.c (13916B)
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1 /*
2 * jdmerge.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 code for merged upsampling/color conversion.
9 *
10 * This file combines functions from jdsample.c and jdcolor.c;
11 * read those files first to understand what's going on.
12 *
13 * When the chroma components are to be upsampled by simple replication
14 * (ie, box filtering), we can save some work in color conversion by
15 * calculating all the output pixels corresponding to a pair of chroma
16 * samples at one time. In the conversion equations
17 * R = Y + K1 * Cr
18 * G = Y + K2 * Cb + K3 * Cr
19 * B = Y + K4 * Cb
20 * only the Y term varies among the group of pixels corresponding to a pair
21 * of chroma samples, so the rest of the terms can be calculated just once.
22 * At typical sampling ratios, this eliminates half or three-quarters of the
23 * multiplications needed for color conversion.
24 *
25 * This file currently provides implementations for the following cases:
26 * YCbCr => RGB color conversion only.
27 * Sampling ratios of 2h1v or 2h2v.
28 * No scaling needed at upsample time.
29 * Corner-aligned (non-CCIR601) sampling alignment.
30 * Other special cases could be added, but in most applications these are
31 * the only common cases. (For uncommon cases we fall back on the more
32 * general code in jdsample.c and jdcolor.c.)
33 */
34
35 #define JPEG_INTERNALS
36 #include "jinclude.h"
37 #include "jpeglib.h"
38
39 #ifdef UPSAMPLE_MERGING_SUPPORTED
40
41
42 /* Private subobject */
43
44 typedef struct {
45 struct jpeg_upsampler pub; /* public fields */
46
47 /* Pointer to routine to do actual upsampling/conversion of one row group */
48 JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
49 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
50 JSAMPARRAY output_buf));
51
52 /* Private state for YCC->RGB conversion */
53 int * Cr_r_tab; /* => table for Cr to R conversion */
54 int * Cb_b_tab; /* => table for Cb to B conversion */
55 INT32 * Cr_g_tab; /* => table for Cr to G conversion */
56 INT32 * Cb_g_tab; /* => table for Cb to G conversion */
57
58 /* For 2:1 vertical sampling, we produce two output rows at a time.
59 * We need a "spare" row buffer to hold the second output row if the
60 * application provides just a one-row buffer; we also use the spare
61 * to discard the dummy last row if the image height is odd.
62 */
63 JSAMPROW spare_row;
64 boolean spare_full; /* T if spare buffer is occupied */
65
66 JDIMENSION out_row_width; /* samples per output row */
67 JDIMENSION rows_to_go; /* counts rows remaining in image */
68 } my_upsampler;
69
70 typedef my_upsampler * my_upsample_ptr;
71
72 #define SCALEBITS 16 /* speediest right-shift on some machines */
73 #define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
74 #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
75
76
77 /*
78 * Initialize tables for YCC->RGB colorspace conversion.
79 * This is taken directly from jdcolor.c; see that file for more info.
80 */
81
82 LOCAL(void)
83 build_ycc_rgb_table (j_decompress_ptr cinfo)
84 {
85 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
86 int i;
87 INT32 x;
88 SHIFT_TEMPS
89
90 upsample->Cr_r_tab = (int *)
91 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
92 (MAXJSAMPLE+1) * SIZEOF(int));
93 upsample->Cb_b_tab = (int *)
94 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
95 (MAXJSAMPLE+1) * SIZEOF(int));
96 upsample->Cr_g_tab = (INT32 *)
97 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
98 (MAXJSAMPLE+1) * SIZEOF(INT32));
99 upsample->Cb_g_tab = (INT32 *)
100 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
101 (MAXJSAMPLE+1) * SIZEOF(INT32));
102
103 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
104 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
105 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
106 /* Cr=>R value is nearest int to 1.40200 * x */
107 upsample->Cr_r_tab[i] = (int)
108 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
109 /* Cb=>B value is nearest int to 1.77200 * x */
110 upsample->Cb_b_tab[i] = (int)
111 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
112 /* Cr=>G value is scaled-up -0.71414 * x */
113 upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
114 /* Cb=>G value is scaled-up -0.34414 * x */
115 /* We also add in ONE_HALF so that need not do it in inner loop */
116 upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
117 }
118 }
119
120
121 /*
122 * Initialize for an upsampling pass.
123 */
124
125 METHODDEF(void)
126 start_pass_merged_upsample (j_decompress_ptr cinfo)
127 {
128 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
129
130 /* Mark the spare buffer empty */
131 upsample->spare_full = FALSE;
132 /* Initialize total-height counter for detecting bottom of image */
133 upsample->rows_to_go = cinfo->output_height;
134 }
135
136
137 /*
138 * Control routine to do upsampling (and color conversion).
139 *
140 * The control routine just handles the row buffering considerations.
141 */
142
143 METHODDEF(void)
144 merged_2v_upsample (j_decompress_ptr cinfo,
145 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
146 JDIMENSION in_row_groups_avail,
147 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
148 JDIMENSION out_rows_avail)
149 /* 2:1 vertical sampling case: may need a spare row. */
150 {
151 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
152 JSAMPROW work_ptrs[2];
153 JDIMENSION num_rows; /* number of rows returned to caller */
154
155 if (upsample->spare_full) {
156 /* If we have a spare row saved from a previous cycle, just return it. */
157 jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
158 1, upsample->out_row_width);
159 num_rows = 1;
160 upsample->spare_full = FALSE;
161 } else {
162 /* Figure number of rows to return to caller. */
163 num_rows = 2;
164 /* Not more than the distance to the end of the image. */
165 if (num_rows > upsample->rows_to_go)
166 num_rows = upsample->rows_to_go;
167 /* And not more than what the client can accept: */
168 out_rows_avail -= *out_row_ctr;
169 if (num_rows > out_rows_avail)
170 num_rows = out_rows_avail;
171 /* Create output pointer array for upsampler. */
172 work_ptrs[0] = output_buf[*out_row_ctr];
173 if (num_rows > 1) {
174 work_ptrs[1] = output_buf[*out_row_ctr + 1];
175 } else {
176 work_ptrs[1] = upsample->spare_row;
177 upsample->spare_full = TRUE;
178 }
179 /* Now do the upsampling. */
180 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
181 }
182
183 /* Adjust counts */
184 *out_row_ctr += num_rows;
185 upsample->rows_to_go -= num_rows;
186 /* When the buffer is emptied, declare this input row group consumed */
187 if (! upsample->spare_full)
188 (*in_row_group_ctr)++;
189 }
190
191
192 METHODDEF(void)
193 merged_1v_upsample (j_decompress_ptr cinfo,
194 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
195 JDIMENSION in_row_groups_avail,
196 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
197 JDIMENSION out_rows_avail)
198 /* 1:1 vertical sampling case: much easier, never need a spare row. */
199 {
200 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
201
202 /* Just do the upsampling. */
203 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
204 output_buf + *out_row_ctr);
205 /* Adjust counts */
206 (*out_row_ctr)++;
207 (*in_row_group_ctr)++;
208 }
209
210
211 /*
212 * These are the routines invoked by the control routines to do
213 * the actual upsampling/conversion. One row group is processed per call.
214 *
215 * Note: since we may be writing directly into application-supplied buffers,
216 * we have to be honest about the output width; we can't assume the buffer
217 * has been rounded up to an even width.
218 */
219
220
221 /*
222 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
223 */
224
225 METHODDEF(void)
226 h2v1_merged_upsample (j_decompress_ptr cinfo,
227 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
228 JSAMPARRAY output_buf)
229 {
230 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
231 register int y, cred, cgreen, cblue;
232 int cb, cr;
233 register JSAMPROW outptr;
234 JSAMPROW inptr0, inptr1, inptr2;
235 JDIMENSION col;
236 /* copy these pointers into registers if possible */
237 register JSAMPLE * range_limit = cinfo->sample_range_limit;
238 int * Crrtab = upsample->Cr_r_tab;
239 int * Cbbtab = upsample->Cb_b_tab;
240 INT32 * Crgtab = upsample->Cr_g_tab;
241 INT32 * Cbgtab = upsample->Cb_g_tab;
242 SHIFT_TEMPS
243
244 inptr0 = input_buf[0][in_row_group_ctr];
245 inptr1 = input_buf[1][in_row_group_ctr];
246 inptr2 = input_buf[2][in_row_group_ctr];
247 outptr = output_buf[0];
248 /* Loop for each pair of output pixels */
249 for (col = cinfo->output_width >> 1; col > 0; col--) {
250 /* Do the chroma part of the calculation */
251 cb = GETJSAMPLE(*inptr1++);
252 cr = GETJSAMPLE(*inptr2++);
253 cred = Crrtab[cr];
254 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
255 cblue = Cbbtab[cb];
256 /* Fetch 2 Y values and emit 2 pixels */
257 y = GETJSAMPLE(*inptr0++);
258 outptr[RGB_RED] = range_limit[y + cred];
259 outptr[RGB_GREEN] = range_limit[y + cgreen];
260 outptr[RGB_BLUE] = range_limit[y + cblue];
261 outptr += RGB_PIXELSIZE;
262 y = GETJSAMPLE(*inptr0++);
263 outptr[RGB_RED] = range_limit[y + cred];
264 outptr[RGB_GREEN] = range_limit[y + cgreen];
265 outptr[RGB_BLUE] = range_limit[y + cblue];
266 outptr += RGB_PIXELSIZE;
267 }
268 /* If image width is odd, do the last output column separately */
269 if (cinfo->output_width & 1) {
270 cb = GETJSAMPLE(*inptr1);
271 cr = GETJSAMPLE(*inptr2);
272 cred = Crrtab[cr];
273 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
274 cblue = Cbbtab[cb];
275 y = GETJSAMPLE(*inptr0);
276 outptr[RGB_RED] = range_limit[y + cred];
277 outptr[RGB_GREEN] = range_limit[y + cgreen];
278 outptr[RGB_BLUE] = range_limit[y + cblue];
279 }
280 }
281
282
283 /*
284 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
285 */
286
287 METHODDEF(void)
288 h2v2_merged_upsample (j_decompress_ptr cinfo,
289 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
290 JSAMPARRAY output_buf)
291 {
292 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
293 register int y, cred, cgreen, cblue;
294 int cb, cr;
295 register JSAMPROW outptr0, outptr1;
296 JSAMPROW inptr00, inptr01, inptr1, inptr2;
297 JDIMENSION col;
298 /* copy these pointers into registers if possible */
299 register JSAMPLE * range_limit = cinfo->sample_range_limit;
300 int * Crrtab = upsample->Cr_r_tab;
301 int * Cbbtab = upsample->Cb_b_tab;
302 INT32 * Crgtab = upsample->Cr_g_tab;
303 INT32 * Cbgtab = upsample->Cb_g_tab;
304 SHIFT_TEMPS
305
306 inptr00 = input_buf[0][in_row_group_ctr*2];
307 inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
308 inptr1 = input_buf[1][in_row_group_ctr];
309 inptr2 = input_buf[2][in_row_group_ctr];
310 outptr0 = output_buf[0];
311 outptr1 = output_buf[1];
312 /* Loop for each group of output pixels */
313 for (col = cinfo->output_width >> 1; col > 0; col--) {
314 /* Do the chroma part of the calculation */
315 cb = GETJSAMPLE(*inptr1++);
316 cr = GETJSAMPLE(*inptr2++);
317 cred = Crrtab[cr];
318 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
319 cblue = Cbbtab[cb];
320 /* Fetch 4 Y values and emit 4 pixels */
321 y = GETJSAMPLE(*inptr00++);
322 outptr0[RGB_RED] = range_limit[y + cred];
323 outptr0[RGB_GREEN] = range_limit[y + cgreen];
324 outptr0[RGB_BLUE] = range_limit[y + cblue];
325 outptr0 += RGB_PIXELSIZE;
326 y = GETJSAMPLE(*inptr00++);
327 outptr0[RGB_RED] = range_limit[y + cred];
328 outptr0[RGB_GREEN] = range_limit[y + cgreen];
329 outptr0[RGB_BLUE] = range_limit[y + cblue];
330 outptr0 += RGB_PIXELSIZE;
331 y = GETJSAMPLE(*inptr01++);
332 outptr1[RGB_RED] = range_limit[y + cred];
333 outptr1[RGB_GREEN] = range_limit[y + cgreen];
334 outptr1[RGB_BLUE] = range_limit[y + cblue];
335 outptr1 += RGB_PIXELSIZE;
336 y = GETJSAMPLE(*inptr01++);
337 outptr1[RGB_RED] = range_limit[y + cred];
338 outptr1[RGB_GREEN] = range_limit[y + cgreen];
339 outptr1[RGB_BLUE] = range_limit[y + cblue];
340 outptr1 += RGB_PIXELSIZE;
341 }
342 /* If image width is odd, do the last output column separately */
343 if (cinfo->output_width & 1) {
344 cb = GETJSAMPLE(*inptr1);
345 cr = GETJSAMPLE(*inptr2);
346 cred = Crrtab[cr];
347 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
348 cblue = Cbbtab[cb];
349 y = GETJSAMPLE(*inptr00);
350 outptr0[RGB_RED] = range_limit[y + cred];
351 outptr0[RGB_GREEN] = range_limit[y + cgreen];
352 outptr0[RGB_BLUE] = range_limit[y + cblue];
353 y = GETJSAMPLE(*inptr01);
354 outptr1[RGB_RED] = range_limit[y + cred];
355 outptr1[RGB_GREEN] = range_limit[y + cgreen];
356 outptr1[RGB_BLUE] = range_limit[y + cblue];
357 }
358 }
359
360
361 /*
362 * Module initialization routine for merged upsampling/color conversion.
363 *
364 * NB: this is called under the conditions determined by use_merged_upsample()
365 * in jdmaster.c. That routine MUST correspond to the actual capabilities
366 * of this module; no safety checks are made here.
367 */
368
369 GLOBAL(void)
370 jinit_merged_upsampler (j_decompress_ptr cinfo)
371 {
372 my_upsample_ptr upsample;
373
374 upsample = (my_upsample_ptr)
375 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
376 SIZEOF(my_upsampler));
377 cinfo->upsample = (struct jpeg_upsampler *) upsample;
378 upsample->pub.start_pass = start_pass_merged_upsample;
379 upsample->pub.need_context_rows = FALSE;
380
381 upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
382
383 if (cinfo->max_v_samp_factor == 2) {
384 upsample->pub.upsample = merged_2v_upsample;
385 upsample->upmethod = h2v2_merged_upsample;
386 /* Allocate a spare row buffer */
387 upsample->spare_row = (JSAMPROW)
388 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
389 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
390 } else {
391 upsample->pub.upsample = merged_1v_upsample;
392 upsample->upmethod = h2v1_merged_upsample;
393 /* No spare row needed */
394 upsample->spare_row = NULL;
395 }
396
397 build_ycc_rgb_table(cinfo);
398 }
399
400 #endif /* UPSAMPLE_MERGING_SUPPORTED */