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)
build_ycc_rgb_table(j_decompress_ptr cinfo)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)
start_pass_merged_upsample(j_decompress_ptr cinfo)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)
merged_2v_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION * in_row_group_ctr,JDIMENSION in_row_groups_avail,JSAMPARRAY output_buf,JDIMENSION * out_row_ctr,JDIMENSION out_rows_avail)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 (void) in_row_groups_avail;
156
157 if (upsample->spare_full) {
158 /* If we have a spare row saved from a previous cycle, just return it. */
159 jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
160 1, upsample->out_row_width);
161 num_rows = 1;
162 upsample->spare_full = FALSE;
163 } else {
164 /* Figure number of rows to return to caller. */
165 num_rows = 2;
166 /* Not more than the distance to the end of the image. */
167 if (num_rows > upsample->rows_to_go)
168 num_rows = upsample->rows_to_go;
169 /* And not more than what the client can accept: */
170 out_rows_avail -= *out_row_ctr;
171 if (num_rows > out_rows_avail)
172 num_rows = out_rows_avail;
173 /* Create output pointer array for upsampler. */
174 work_ptrs[0] = output_buf[*out_row_ctr];
175 if (num_rows > 1) {
176 work_ptrs[1] = output_buf[*out_row_ctr + 1];
177 } else {
178 work_ptrs[1] = upsample->spare_row;
179 upsample->spare_full = TRUE;
180 }
181 /* Now do the upsampling. */
182 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
183 }
184
185 /* Adjust counts */
186 *out_row_ctr += num_rows;
187 upsample->rows_to_go -= num_rows;
188 /* When the buffer is emptied, declare this input row group consumed */
189 if (! upsample->spare_full)
190 (*in_row_group_ctr)++;
191 }
192
193
194 METHODDEF(void)
merged_1v_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION * in_row_group_ctr,JDIMENSION in_row_groups_avail,JSAMPARRAY output_buf,JDIMENSION * out_row_ctr,JDIMENSION out_rows_avail)195 merged_1v_upsample (j_decompress_ptr cinfo,
196 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
197 JDIMENSION in_row_groups_avail,
198 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
199 JDIMENSION out_rows_avail)
200 /* 1:1 vertical sampling case: much easier, never need a spare row. */
201 {
202 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
203
204 (void) in_row_groups_avail;
205 (void) out_rows_avail;
206
207 /* Just do the upsampling. */
208 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
209 output_buf + *out_row_ctr);
210 /* Adjust counts */
211 (*out_row_ctr)++;
212 (*in_row_group_ctr)++;
213 }
214
215
216 /*
217 * These are the routines invoked by the control routines to do
218 * the actual upsampling/conversion. One row group is processed per call.
219 *
220 * Note: since we may be writing directly into application-supplied buffers,
221 * we have to be honest about the output width; we can't assume the buffer
222 * has been rounded up to an even width.
223 */
224
225
226 /*
227 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
228 */
229
230 METHODDEF(void)
h2v1_merged_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION in_row_group_ctr,JSAMPARRAY output_buf)231 h2v1_merged_upsample (j_decompress_ptr cinfo,
232 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
233 JSAMPARRAY output_buf)
234 {
235 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
236 register int y, cred, cgreen, cblue;
237 int cb, cr;
238 register JSAMPROW outptr;
239 JSAMPROW inptr0, inptr1, inptr2;
240 JDIMENSION col;
241 /* copy these pointers into registers if possible */
242 register JSAMPLE * range_limit = cinfo->sample_range_limit;
243 int * Crrtab = upsample->Cr_r_tab;
244 int * Cbbtab = upsample->Cb_b_tab;
245 INT32 * Crgtab = upsample->Cr_g_tab;
246 INT32 * Cbgtab = upsample->Cb_g_tab;
247 SHIFT_TEMPS
248
249 inptr0 = input_buf[0][in_row_group_ctr];
250 inptr1 = input_buf[1][in_row_group_ctr];
251 inptr2 = input_buf[2][in_row_group_ctr];
252 outptr = output_buf[0];
253 /* Loop for each pair of output pixels */
254 for (col = cinfo->output_width >> 1; col > 0; col--) {
255 /* Do the chroma part of the calculation */
256 cb = GETJSAMPLE(*inptr1++);
257 cr = GETJSAMPLE(*inptr2++);
258 cred = Crrtab[cr];
259 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
260 cblue = Cbbtab[cb];
261 /* Fetch 2 Y values and emit 2 pixels */
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 y = GETJSAMPLE(*inptr0++);
268 outptr[RGB_RED] = range_limit[y + cred];
269 outptr[RGB_GREEN] = range_limit[y + cgreen];
270 outptr[RGB_BLUE] = range_limit[y + cblue];
271 outptr += RGB_PIXELSIZE;
272 }
273 /* If image width is odd, do the last output column separately */
274 if (cinfo->output_width & 1) {
275 cb = GETJSAMPLE(*inptr1);
276 cr = GETJSAMPLE(*inptr2);
277 cred = Crrtab[cr];
278 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
279 cblue = Cbbtab[cb];
280 y = GETJSAMPLE(*inptr0);
281 outptr[RGB_RED] = range_limit[y + cred];
282 outptr[RGB_GREEN] = range_limit[y + cgreen];
283 outptr[RGB_BLUE] = range_limit[y + cblue];
284 }
285 }
286
287
288 /*
289 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
290 */
291
292 METHODDEF(void)
h2v2_merged_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION in_row_group_ctr,JSAMPARRAY output_buf)293 h2v2_merged_upsample (j_decompress_ptr cinfo,
294 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
295 JSAMPARRAY output_buf)
296 {
297 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
298 register int y, cred, cgreen, cblue;
299 int cb, cr;
300 register JSAMPROW outptr0, outptr1;
301 JSAMPROW inptr00, inptr01, inptr1, inptr2;
302 JDIMENSION col;
303 /* copy these pointers into registers if possible */
304 register JSAMPLE * range_limit = cinfo->sample_range_limit;
305 int * Crrtab = upsample->Cr_r_tab;
306 int * Cbbtab = upsample->Cb_b_tab;
307 INT32 * Crgtab = upsample->Cr_g_tab;
308 INT32 * Cbgtab = upsample->Cb_g_tab;
309 SHIFT_TEMPS
310
311 inptr00 = input_buf[0][in_row_group_ctr*2];
312 inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
313 inptr1 = input_buf[1][in_row_group_ctr];
314 inptr2 = input_buf[2][in_row_group_ctr];
315 outptr0 = output_buf[0];
316 outptr1 = output_buf[1];
317 /* Loop for each group of output pixels */
318 for (col = cinfo->output_width >> 1; col > 0; col--) {
319 /* Do the chroma part of the calculation */
320 cb = GETJSAMPLE(*inptr1++);
321 cr = GETJSAMPLE(*inptr2++);
322 cred = Crrtab[cr];
323 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
324 cblue = Cbbtab[cb];
325 /* Fetch 4 Y values and emit 4 pixels */
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(*inptr00++);
332 outptr0[RGB_RED] = range_limit[y + cred];
333 outptr0[RGB_GREEN] = range_limit[y + cgreen];
334 outptr0[RGB_BLUE] = range_limit[y + cblue];
335 outptr0 += 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 y = GETJSAMPLE(*inptr01++);
342 outptr1[RGB_RED] = range_limit[y + cred];
343 outptr1[RGB_GREEN] = range_limit[y + cgreen];
344 outptr1[RGB_BLUE] = range_limit[y + cblue];
345 outptr1 += RGB_PIXELSIZE;
346 }
347 /* If image width is odd, do the last output column separately */
348 if (cinfo->output_width & 1) {
349 cb = GETJSAMPLE(*inptr1);
350 cr = GETJSAMPLE(*inptr2);
351 cred = Crrtab[cr];
352 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
353 cblue = Cbbtab[cb];
354 y = GETJSAMPLE(*inptr00);
355 outptr0[RGB_RED] = range_limit[y + cred];
356 outptr0[RGB_GREEN] = range_limit[y + cgreen];
357 outptr0[RGB_BLUE] = range_limit[y + cblue];
358 y = GETJSAMPLE(*inptr01);
359 outptr1[RGB_RED] = range_limit[y + cred];
360 outptr1[RGB_GREEN] = range_limit[y + cgreen];
361 outptr1[RGB_BLUE] = range_limit[y + cblue];
362 }
363 }
364
365
366 /*
367 * Module initialization routine for merged upsampling/color conversion.
368 *
369 * NB: this is called under the conditions determined by use_merged_upsample()
370 * in jdmaster.c. That routine MUST correspond to the actual capabilities
371 * of this module; no safety checks are made here.
372 */
373
374 GLOBAL(void)
jinit_merged_upsampler(j_decompress_ptr cinfo)375 jinit_merged_upsampler (j_decompress_ptr cinfo)
376 {
377 my_upsample_ptr upsample;
378
379 upsample = (my_upsample_ptr)
380 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
381 SIZEOF(my_upsampler));
382 cinfo->upsample = (struct jpeg_upsampler *) upsample;
383 upsample->pub.start_pass = start_pass_merged_upsample;
384 upsample->pub.need_context_rows = FALSE;
385
386 upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
387
388 if (cinfo->max_v_samp_factor == 2) {
389 upsample->pub.upsample = merged_2v_upsample;
390 upsample->upmethod = h2v2_merged_upsample;
391 /* Allocate a spare row buffer */
392 upsample->spare_row = (JSAMPROW)
393 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
394 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
395 } else {
396 upsample->pub.upsample = merged_1v_upsample;
397 upsample->upmethod = h2v1_merged_upsample;
398 /* No spare row needed */
399 upsample->spare_row = NULL;
400 }
401
402 build_ycc_rgb_table(cinfo);
403 }
404
405 #endif /* UPSAMPLE_MERGING_SUPPORTED */
406