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jdsample.c (16381B)
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1 /*
2 * jdsample.c
3 *
4 * Copyright (C) 1991-1996, 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 upsampling routines.
9 *
10 * Upsampling input data is counted in "row groups". A row group
11 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
12 * sample rows of each component. Upsampling will normally produce
13 * max_v_samp_factor pixel rows from each row group (but this could vary
14 * if the upsampler is applying a scale factor of its own).
15 *
16 * An excellent reference for image resampling is
17 * Digital Image Warping, George Wolberg, 1990.
18 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
19 */
20
21 #define JPEG_INTERNALS
22 #include "jinclude.h"
23 #include "jpeglib.h"
24
25
26 /* Pointer to routine to upsample a single component */
27 typedef JMETHOD(void, upsample1_ptr,
28 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
29 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
30
31 /* Private subobject */
32
33 typedef struct {
34 struct jpeg_upsampler pub; /* public fields */
35
36 /* Color conversion buffer. When using separate upsampling and color
37 * conversion steps, this buffer holds one upsampled row group until it
38 * has been color converted and output.
39 * Note: we do not allocate any storage for component(s) which are full-size,
40 * ie do not need rescaling. The corresponding entry of color_buf[] is
41 * simply set to point to the input data array, thereby avoiding copying.
42 */
43 JSAMPARRAY color_buf[MAX_COMPONENTS];
44
45 /* Per-component upsampling method pointers */
46 upsample1_ptr methods[MAX_COMPONENTS];
47
48 int next_row_out; /* counts rows emitted from color_buf */
49 JDIMENSION rows_to_go; /* counts rows remaining in image */
50
51 /* Height of an input row group for each component. */
52 int rowgroup_height[MAX_COMPONENTS];
53
54 /* These arrays save pixel expansion factors so that int_expand need not
55 * recompute them each time. They are unused for other upsampling methods.
56 */
57 UINT8 h_expand[MAX_COMPONENTS];
58 UINT8 v_expand[MAX_COMPONENTS];
59 } my_upsampler;
60
61 typedef my_upsampler * my_upsample_ptr;
62
63
64 /*
65 * Initialize for an upsampling pass.
66 */
67
68 METHODDEF(void)
69 start_pass_upsample (j_decompress_ptr cinfo)
70 {
71 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
72
73 /* Mark the conversion buffer empty */
74 upsample->next_row_out = cinfo->max_v_samp_factor;
75 /* Initialize total-height counter for detecting bottom of image */
76 upsample->rows_to_go = cinfo->output_height;
77 }
78
79
80 /*
81 * Control routine to do upsampling (and color conversion).
82 *
83 * In this version we upsample each component independently.
84 * We upsample one row group into the conversion buffer, then apply
85 * color conversion a row at a time.
86 */
87
88 METHODDEF(void)
89 sep_upsample (j_decompress_ptr cinfo,
90 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
91 JDIMENSION in_row_groups_avail,
92 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
93 JDIMENSION out_rows_avail)
94 {
95 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
96 int ci;
97 jpeg_component_info * compptr;
98 JDIMENSION num_rows;
99
100 /* Fill the conversion buffer, if it's empty */
101 if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
102 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
103 ci++, compptr++) {
104 /* Invoke per-component upsample method. Notice we pass a POINTER
105 * to color_buf[ci], so that fullsize_upsample can change it.
106 */
107 (*upsample->methods[ci]) (cinfo, compptr,
108 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
109 upsample->color_buf + ci);
110 }
111 upsample->next_row_out = 0;
112 }
113
114 /* Color-convert and emit rows */
115
116 /* How many we have in the buffer: */
117 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
118 /* Not more than the distance to the end of the image. Need this test
119 * in case the image height is not a multiple of max_v_samp_factor:
120 */
121 if (num_rows > upsample->rows_to_go)
122 num_rows = upsample->rows_to_go;
123 /* And not more than what the client can accept: */
124 out_rows_avail -= *out_row_ctr;
125 if (num_rows > out_rows_avail)
126 num_rows = out_rows_avail;
127
128 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
129 (JDIMENSION) upsample->next_row_out,
130 output_buf + *out_row_ctr,
131 (int) num_rows);
132
133 /* Adjust counts */
134 *out_row_ctr += num_rows;
135 upsample->rows_to_go -= num_rows;
136 upsample->next_row_out += num_rows;
137 /* When the buffer is emptied, declare this input row group consumed */
138 if (upsample->next_row_out >= cinfo->max_v_samp_factor)
139 (*in_row_group_ctr)++;
140 }
141
142
143 /*
144 * These are the routines invoked by sep_upsample to upsample pixel values
145 * of a single component. One row group is processed per call.
146 */
147
148
149 /*
150 * For full-size components, we just make color_buf[ci] point at the
151 * input buffer, and thus avoid copying any data. Note that this is
152 * safe only because sep_upsample doesn't declare the input row group
153 * "consumed" until we are done color converting and emitting it.
154 */
155
156 METHODDEF(void)
157 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
158 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
159 {
160 *output_data_ptr = input_data;
161 }
162
163
164 /*
165 * This is a no-op version used for "uninteresting" components.
166 * These components will not be referenced by color conversion.
167 */
168
169 METHODDEF(void)
170 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
171 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
172 {
173 *output_data_ptr = NULL; /* safety check */
174 }
175
176
177 /*
178 * This version handles any integral sampling ratios.
179 * This is not used for typical JPEG files, so it need not be fast.
180 * Nor, for that matter, is it particularly accurate: the algorithm is
181 * simple replication of the input pixel onto the corresponding output
182 * pixels. The hi-falutin sampling literature refers to this as a
183 * "box filter". A box filter tends to introduce visible artifacts,
184 * so if you are actually going to use 3:1 or 4:1 sampling ratios
185 * you would be well advised to improve this code.
186 */
187
188 METHODDEF(void)
189 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
190 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
191 {
192 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
193 JSAMPARRAY output_data = *output_data_ptr;
194 register JSAMPROW inptr, outptr;
195 register JSAMPLE invalue;
196 register int h;
197 JSAMPROW outend;
198 int h_expand, v_expand;
199 int inrow, outrow;
200
201 h_expand = upsample->h_expand[compptr->component_index];
202 v_expand = upsample->v_expand[compptr->component_index];
203
204 inrow = outrow = 0;
205 while (outrow < cinfo->max_v_samp_factor) {
206 /* Generate one output row with proper horizontal expansion */
207 inptr = input_data[inrow];
208 outptr = output_data[outrow];
209 outend = outptr + cinfo->output_width;
210 while (outptr < outend) {
211 invalue = *inptr++; /* don't need GETJSAMPLE() here */
212 for (h = h_expand; h > 0; h--) {
213 *outptr++ = invalue;
214 }
215 }
216 /* Generate any additional output rows by duplicating the first one */
217 if (v_expand > 1) {
218 jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
219 v_expand-1, cinfo->output_width);
220 }
221 inrow++;
222 outrow += v_expand;
223 }
224 }
225
226
227 /*
228 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
229 * It's still a box filter.
230 */
231
232 METHODDEF(void)
233 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
234 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
235 {
236 JSAMPARRAY output_data = *output_data_ptr;
237 register JSAMPROW inptr, outptr;
238 register JSAMPLE invalue;
239 JSAMPROW outend;
240 int inrow;
241
242 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
243 inptr = input_data[inrow];
244 outptr = output_data[inrow];
245 outend = outptr + cinfo->output_width;
246 while (outptr < outend) {
247 invalue = *inptr++; /* don't need GETJSAMPLE() here */
248 *outptr++ = invalue;
249 *outptr++ = invalue;
250 }
251 }
252 }
253
254
255 /*
256 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
257 * It's still a box filter.
258 */
259
260 METHODDEF(void)
261 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
262 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
263 {
264 JSAMPARRAY output_data = *output_data_ptr;
265 register JSAMPROW inptr, outptr;
266 register JSAMPLE invalue;
267 JSAMPROW outend;
268 int inrow, outrow;
269
270 inrow = outrow = 0;
271 while (outrow < cinfo->max_v_samp_factor) {
272 inptr = input_data[inrow];
273 outptr = output_data[outrow];
274 outend = outptr + cinfo->output_width;
275 while (outptr < outend) {
276 invalue = *inptr++; /* don't need GETJSAMPLE() here */
277 *outptr++ = invalue;
278 *outptr++ = invalue;
279 }
280 jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
281 1, cinfo->output_width);
282 inrow++;
283 outrow += 2;
284 }
285 }
286
287
288 /*
289 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
290 *
291 * The upsampling algorithm is linear interpolation between pixel centers,
292 * also known as a "triangle filter". This is a good compromise between
293 * speed and visual quality. The centers of the output pixels are 1/4 and 3/4
294 * of the way between input pixel centers.
295 *
296 * A note about the "bias" calculations: when rounding fractional values to
297 * integer, we do not want to always round 0.5 up to the next integer.
298 * If we did that, we'd introduce a noticeable bias towards larger values.
299 * Instead, this code is arranged so that 0.5 will be rounded up or down at
300 * alternate pixel locations (a simple ordered dither pattern).
301 */
302
303 METHODDEF(void)
304 h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
305 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
306 {
307 JSAMPARRAY output_data = *output_data_ptr;
308 register JSAMPROW inptr, outptr;
309 register int invalue;
310 register JDIMENSION colctr;
311 int inrow;
312
313 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
314 inptr = input_data[inrow];
315 outptr = output_data[inrow];
316 /* Special case for first column */
317 invalue = GETJSAMPLE(*inptr++);
318 *outptr++ = (JSAMPLE) invalue;
319 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
320
321 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
322 /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
323 invalue = GETJSAMPLE(*inptr++) * 3;
324 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
325 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
326 }
327
328 /* Special case for last column */
329 invalue = GETJSAMPLE(*inptr);
330 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
331 *outptr++ = (JSAMPLE) invalue;
332 }
333 }
334
335
336 /*
337 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
338 * Again a triangle filter; see comments for h2v1 case, above.
339 *
340 * It is OK for us to reference the adjacent input rows because we demanded
341 * context from the main buffer controller (see initialization code).
342 */
343
344 METHODDEF(void)
345 h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
346 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
347 {
348 JSAMPARRAY output_data = *output_data_ptr;
349 register JSAMPROW inptr0, inptr1, outptr;
350 #if BITS_IN_JSAMPLE == 8
351 register int thiscolsum, lastcolsum, nextcolsum;
352 #else
353 register INT32 thiscolsum, lastcolsum, nextcolsum;
354 #endif
355 register JDIMENSION colctr;
356 int inrow, outrow, v;
357
358 inrow = outrow = 0;
359 while (outrow < cinfo->max_v_samp_factor) {
360 for (v = 0; v < 2; v++) {
361 /* inptr0 points to nearest input row, inptr1 points to next nearest */
362 inptr0 = input_data[inrow];
363 if (v == 0) /* next nearest is row above */
364 inptr1 = input_data[inrow-1];
365 else /* next nearest is row below */
366 inptr1 = input_data[inrow+1];
367 outptr = output_data[outrow++];
368
369 /* Special case for first column */
370 thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
371 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
372 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
373 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
374 lastcolsum = thiscolsum; thiscolsum = nextcolsum;
375
376 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
377 /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
378 /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
379 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
380 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
381 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
382 lastcolsum = thiscolsum; thiscolsum = nextcolsum;
383 }
384
385 /* Special case for last column */
386 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
387 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
388 }
389 inrow++;
390 }
391 }
392
393
394 /*
395 * Module initialization routine for upsampling.
396 */
397
398 GLOBAL(void)
399 jinit_upsampler (j_decompress_ptr cinfo)
400 {
401 my_upsample_ptr upsample;
402 int ci;
403 jpeg_component_info * compptr;
404 boolean need_buffer, do_fancy;
405 int h_in_group, v_in_group, h_out_group, v_out_group;
406
407 upsample = (my_upsample_ptr)
408 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
409 SIZEOF(my_upsampler));
410 cinfo->upsample = (struct jpeg_upsampler *) upsample;
411 upsample->pub.start_pass = start_pass_upsample;
412 upsample->pub.upsample = sep_upsample;
413 upsample->pub.need_context_rows = FALSE; /* until we find out differently */
414
415 if (cinfo->CCIR601_sampling) /* this isn't supported */
416 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
417
418 /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
419 * so don't ask for it.
420 */
421 do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;
422
423 /* Verify we can handle the sampling factors, select per-component methods,
424 * and create storage as needed.
425 */
426 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
427 ci++, compptr++) {
428 /* Compute size of an "input group" after IDCT scaling. This many samples
429 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
430 */
431 h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /
432 cinfo->min_DCT_scaled_size;
433 v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
434 cinfo->min_DCT_scaled_size;
435 h_out_group = cinfo->max_h_samp_factor;
436 v_out_group = cinfo->max_v_samp_factor;
437 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
438 need_buffer = TRUE;
439 if (! compptr->component_needed) {
440 /* Don't bother to upsample an uninteresting component. */
441 upsample->methods[ci] = noop_upsample;
442 need_buffer = FALSE;
443 } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
444 /* Fullsize components can be processed without any work. */
445 upsample->methods[ci] = fullsize_upsample;
446 need_buffer = FALSE;
447 } else if (h_in_group * 2 == h_out_group &&
448 v_in_group == v_out_group) {
449 /* Special cases for 2h1v upsampling */
450 if (do_fancy && compptr->downsampled_width > 2)
451 upsample->methods[ci] = h2v1_fancy_upsample;
452 else
453 upsample->methods[ci] = h2v1_upsample;
454 } else if (h_in_group * 2 == h_out_group &&
455 v_in_group * 2 == v_out_group) {
456 /* Special cases for 2h2v upsampling */
457 if (do_fancy && compptr->downsampled_width > 2) {
458 upsample->methods[ci] = h2v2_fancy_upsample;
459 upsample->pub.need_context_rows = TRUE;
460 } else
461 upsample->methods[ci] = h2v2_upsample;
462 } else if ((h_out_group % h_in_group) == 0 &&
463 (v_out_group % v_in_group) == 0) {
464 /* Generic integral-factors upsampling method */
465 upsample->methods[ci] = int_upsample;
466 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
467 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
468 } else
469 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
470 if (need_buffer) {
471 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
472 ((j_common_ptr) cinfo, JPOOL_IMAGE,
473 (JDIMENSION) jround_up((long) cinfo->output_width,
474 (long) cinfo->max_h_samp_factor),
475 (JDIMENSION) cinfo->max_v_samp_factor);
476 }
477 }
478 }