1 /*
2 * jdmerge.c
3 *
4 * Copyright (C) 1994, 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 for an upsampling pass.
79 */
80
81 METHODDEF void
start_pass_merged_upsample(j_decompress_ptr cinfo)82 start_pass_merged_upsample (j_decompress_ptr cinfo)
83 {
84 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
85 INT32 i, x;
86 SHIFT_TEMPS
87
88 /* Mark the spare buffer empty */
89 upsample->spare_full = FALSE;
90 /* Initialize total-height counter for detecting bottom of image */
91 upsample->rows_to_go = cinfo->output_height;
92
93 /* Initialize the YCC=>RGB conversion tables.
94 * This is taken directly from jdcolor.c; see that file for more info.
95 */
96 upsample->Cr_r_tab = (int *)
97 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
98 (MAXJSAMPLE+1) * SIZEOF(int));
99 upsample->Cb_b_tab = (int *)
100 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
101 (MAXJSAMPLE+1) * SIZEOF(int));
102 upsample->Cr_g_tab = (INT32 *)
103 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
104 (MAXJSAMPLE+1) * SIZEOF(INT32));
105 upsample->Cb_g_tab = (INT32 *)
106 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
107 (MAXJSAMPLE+1) * SIZEOF(INT32));
108
109 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
110 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
111 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
112 /* Cr=>R value is nearest int to 1.40200 * x */
113 upsample->Cr_r_tab[i] = (int)
114 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
115 /* Cb=>B value is nearest int to 1.77200 * x */
116 upsample->Cb_b_tab[i] = (int)
117 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
118 /* Cr=>G value is scaled-up -0.71414 * x */
119 upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
120 /* Cb=>G value is scaled-up -0.34414 * x */
121 /* We also add in ONE_HALF so that need not do it in inner loop */
122 upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
123 }
124 }
125
126
127 /*
128 * Control routine to do upsampling (and color conversion).
129 *
130 * The control routine just handles the row buffering considerations.
131 */
132
133 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)134 merged_2v_upsample (j_decompress_ptr cinfo,
135 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
136 JDIMENSION in_row_groups_avail,
137 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
138 JDIMENSION out_rows_avail)
139 /* 2:1 vertical sampling case: may need a spare row. */
140 {
141 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
142 JSAMPROW work_ptrs[2];
143 JDIMENSION num_rows; /* number of rows returned to caller */
144
145 if (upsample->spare_full) {
146 /* If we have a spare row saved from a previous cycle, just return it. */
147 jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
148 1, upsample->out_row_width);
149 num_rows = 1;
150 upsample->spare_full = FALSE;
151 } else {
152 /* Figure number of rows to return to caller. */
153 num_rows = 2;
154 /* Not more than the distance to the end of the image. */
155 if (num_rows > upsample->rows_to_go)
156 num_rows = upsample->rows_to_go;
157 /* And not more than what the client can accept: */
158 out_rows_avail -= *out_row_ctr;
159 if (num_rows > out_rows_avail)
160 num_rows = out_rows_avail;
161 /* Create output pointer array for upsampler. */
162 work_ptrs[0] = output_buf[*out_row_ctr];
163 if (num_rows > 1) {
164 work_ptrs[1] = output_buf[*out_row_ctr + 1];
165 } else {
166 work_ptrs[1] = upsample->spare_row;
167 upsample->spare_full = TRUE;
168 }
169 /* Now do the upsampling. */
170 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
171 }
172
173 /* Adjust counts */
174 *out_row_ctr += num_rows;
175 upsample->rows_to_go -= num_rows;
176 /* When the buffer is emptied, declare this input row group consumed */
177 if (! upsample->spare_full)
178 (*in_row_group_ctr)++;
179 }
180
181
182 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)183 merged_1v_upsample (j_decompress_ptr cinfo,
184 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
185 JDIMENSION in_row_groups_avail,
186 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
187 JDIMENSION out_rows_avail)
188 /* 1:1 vertical sampling case: much easier, never need a spare row. */
189 {
190 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
191
192 /* Just do the upsampling. */
193 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
194 output_buf + *out_row_ctr);
195 /* Adjust counts */
196 (*out_row_ctr)++;
197 (*in_row_group_ctr)++;
198 }
199
200
201 /*
202 * These are the routines invoked by the control routines to do
203 * the actual upsampling/conversion. One row group is processed per call.
204 *
205 * Note: since we may be writing directly into application-supplied buffers,
206 * we have to be honest about the output width; we can't assume the buffer
207 * has been rounded up to an even width.
208 */
209
210
211 /*
212 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
213 */
214
215 METHODDEF void
h2v1_merged_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION in_row_group_ctr,JSAMPARRAY output_buf)216 h2v1_merged_upsample (j_decompress_ptr cinfo,
217 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
218 JSAMPARRAY output_buf)
219 {
220 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
221 register int y, cred, cgreen, cblue;
222 int cb, cr;
223 register JSAMPROW outptr;
224 JSAMPROW inptr0, inptr1, inptr2;
225 JDIMENSION col;
226 /* copy these pointers into registers if possible */
227 register JSAMPLE * range_limit = cinfo->sample_range_limit;
228 int * Crrtab = upsample->Cr_r_tab;
229 int * Cbbtab = upsample->Cb_b_tab;
230 INT32 * Crgtab = upsample->Cr_g_tab;
231 INT32 * Cbgtab = upsample->Cb_g_tab;
232 SHIFT_TEMPS
233
234 inptr0 = input_buf[0][in_row_group_ctr];
235 inptr1 = input_buf[1][in_row_group_ctr];
236 inptr2 = input_buf[2][in_row_group_ctr];
237 outptr = output_buf[0];
238 /* Loop for each pair of output pixels */
239 for (col = cinfo->output_width >> 1; col > 0; col--) {
240 /* Do the chroma part of the calculation */
241 cb = GETJSAMPLE(*inptr1++);
242 cr = GETJSAMPLE(*inptr2++);
243 cred = Crrtab[cr];
244 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
245 cblue = Cbbtab[cb];
246 /* Fetch 2 Y values and emit 2 pixels */
247 y = GETJSAMPLE(*inptr0++);
248 outptr[RGB_RED] = range_limit[y + cred];
249 outptr[RGB_GREEN] = range_limit[y + cgreen];
250 outptr[RGB_BLUE] = range_limit[y + cblue];
251 outptr += RGB_PIXELSIZE;
252 y = GETJSAMPLE(*inptr0++);
253 outptr[RGB_RED] = range_limit[y + cred];
254 outptr[RGB_GREEN] = range_limit[y + cgreen];
255 outptr[RGB_BLUE] = range_limit[y + cblue];
256 outptr += RGB_PIXELSIZE;
257 }
258 /* If image width is odd, do the last output column separately */
259 if (cinfo->output_width & 1) {
260 cb = GETJSAMPLE(*inptr1);
261 cr = GETJSAMPLE(*inptr2);
262 cred = Crrtab[cr];
263 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
264 cblue = Cbbtab[cb];
265 y = GETJSAMPLE(*inptr0);
266 outptr[RGB_RED] = range_limit[y + cred];
267 outptr[RGB_GREEN] = range_limit[y + cgreen];
268 outptr[RGB_BLUE] = range_limit[y + cblue];
269 }
270 }
271
272
273 /*
274 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
275 */
276
277 METHODDEF void
h2v2_merged_upsample(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION in_row_group_ctr,JSAMPARRAY output_buf)278 h2v2_merged_upsample (j_decompress_ptr cinfo,
279 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
280 JSAMPARRAY output_buf)
281 {
282 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
283 register int y, cred, cgreen, cblue;
284 int cb, cr;
285 register JSAMPROW outptr0, outptr1;
286 JSAMPROW inptr00, inptr01, inptr1, inptr2;
287 JDIMENSION col;
288 /* copy these pointers into registers if possible */
289 register JSAMPLE * range_limit = cinfo->sample_range_limit;
290 int * Crrtab = upsample->Cr_r_tab;
291 int * Cbbtab = upsample->Cb_b_tab;
292 INT32 * Crgtab = upsample->Cr_g_tab;
293 INT32 * Cbgtab = upsample->Cb_g_tab;
294 SHIFT_TEMPS
295
296 inptr00 = input_buf[0][in_row_group_ctr*2];
297 inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
298 inptr1 = input_buf[1][in_row_group_ctr];
299 inptr2 = input_buf[2][in_row_group_ctr];
300 outptr0 = output_buf[0];
301 outptr1 = output_buf[1];
302 /* Loop for each group of output pixels */
303 for (col = cinfo->output_width >> 1; col > 0; col--) {
304 /* Do the chroma part of the calculation */
305 cb = GETJSAMPLE(*inptr1++);
306 cr = GETJSAMPLE(*inptr2++);
307 cred = Crrtab[cr];
308 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
309 cblue = Cbbtab[cb];
310 /* Fetch 4 Y values and emit 4 pixels */
311 y = GETJSAMPLE(*inptr00++);
312 outptr0[RGB_RED] = range_limit[y + cred];
313 outptr0[RGB_GREEN] = range_limit[y + cgreen];
314 outptr0[RGB_BLUE] = range_limit[y + cblue];
315 outptr0 += RGB_PIXELSIZE;
316 y = GETJSAMPLE(*inptr00++);
317 outptr0[RGB_RED] = range_limit[y + cred];
318 outptr0[RGB_GREEN] = range_limit[y + cgreen];
319 outptr0[RGB_BLUE] = range_limit[y + cblue];
320 outptr0 += RGB_PIXELSIZE;
321 y = GETJSAMPLE(*inptr01++);
322 outptr1[RGB_RED] = range_limit[y + cred];
323 outptr1[RGB_GREEN] = range_limit[y + cgreen];
324 outptr1[RGB_BLUE] = range_limit[y + cblue];
325 outptr1 += RGB_PIXELSIZE;
326 y = GETJSAMPLE(*inptr01++);
327 outptr1[RGB_RED] = range_limit[y + cred];
328 outptr1[RGB_GREEN] = range_limit[y + cgreen];
329 outptr1[RGB_BLUE] = range_limit[y + cblue];
330 outptr1 += RGB_PIXELSIZE;
331 }
332 /* If image width is odd, do the last output column separately */
333 if (cinfo->output_width & 1) {
334 cb = GETJSAMPLE(*inptr1);
335 cr = GETJSAMPLE(*inptr2);
336 cred = Crrtab[cr];
337 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
338 cblue = Cbbtab[cb];
339 y = GETJSAMPLE(*inptr00);
340 outptr0[RGB_RED] = range_limit[y + cred];
341 outptr0[RGB_GREEN] = range_limit[y + cgreen];
342 outptr0[RGB_BLUE] = range_limit[y + cblue];
343 y = GETJSAMPLE(*inptr01);
344 outptr1[RGB_RED] = range_limit[y + cred];
345 outptr1[RGB_GREEN] = range_limit[y + cgreen];
346 outptr1[RGB_BLUE] = range_limit[y + cblue];
347 }
348 }
349
350
351 /*
352 * Module initialization routine for merged upsampling/color conversion.
353 *
354 * NB: this is called under the conditions determined by use_merged_upsample()
355 * in jdmaster.c. That routine MUST correspond to the actual capabilities
356 * of this module; no safety checks are made here.
357 */
358
359 GLOBAL void
jinit_merged_upsampler(j_decompress_ptr cinfo)360 jinit_merged_upsampler (j_decompress_ptr cinfo)
361 {
362 my_upsample_ptr upsample;
363
364 upsample = (my_upsample_ptr)
365 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
366 SIZEOF(my_upsampler));
367 cinfo->upsample = (struct jpeg_upsampler *) upsample;
368 upsample->pub.start_pass = start_pass_merged_upsample;
369 upsample->pub.need_context_rows = FALSE;
370
371 upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
372
373 if (cinfo->max_v_samp_factor == 2) {
374 upsample->pub.upsample = merged_2v_upsample;
375 upsample->upmethod = h2v2_merged_upsample;
376 /* Allocate a spare row buffer */
377 upsample->spare_row = (JSAMPROW)
378 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
379 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
380 } else {
381 upsample->pub.upsample = merged_1v_upsample;
382 upsample->upmethod = h2v1_merged_upsample;
383 /* No spare row needed */
384 upsample->spare_row = NULL;
385 }
386 }
387
388 #endif /* UPSAMPLE_MERGING_SUPPORTED */
389