4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1991-1996, Thomas G. Lane.
6 * libjpeg-turbo Modifications:
7 * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
8 * Copyright (C) 2010, D. R. Commander.
9 * For conditions of distribution and use, see the accompanying README file.
11 * This file contains upsampling routines.
13 * Upsampling input data is counted in "row groups". A row group
14 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
15 * sample rows of each component. Upsampling will normally produce
16 * max_v_samp_factor pixel rows from each row group (but this could vary
17 * if the upsampler is applying a scale factor of its own).
19 * An excellent reference for image resampling is
20 * Digital Image Warping, George Wolberg, 1990.
21 * Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
24 #define JPEG_INTERNALS
31 /* Pointer to routine to upsample a single component */
32 typedef JMETHOD(void, upsample1_ptr,
33 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
34 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
36 /* Private subobject */
39 struct jpeg_upsampler pub; /* public fields */
41 /* Color conversion buffer. When using separate upsampling and color
42 * conversion steps, this buffer holds one upsampled row group until it
43 * has been color converted and output.
44 * Note: we do not allocate any storage for component(s) which are full-size,
45 * ie do not need rescaling. The corresponding entry of color_buf[] is
46 * simply set to point to the input data array, thereby avoiding copying.
48 JSAMPARRAY color_buf[MAX_COMPONENTS];
50 /* Per-component upsampling method pointers */
51 upsample1_ptr methods[MAX_COMPONENTS];
53 int next_row_out; /* counts rows emitted from color_buf */
54 JDIMENSION rows_to_go; /* counts rows remaining in image */
56 /* Height of an input row group for each component. */
57 int rowgroup_height[MAX_COMPONENTS];
59 /* These arrays save pixel expansion factors so that int_expand need not
60 * recompute them each time. They are unused for other upsampling methods.
62 UINT8 h_expand[MAX_COMPONENTS];
63 UINT8 v_expand[MAX_COMPONENTS];
66 typedef my_upsampler * my_upsample_ptr;
70 * Initialize for an upsampling pass.
74 start_pass_upsample (j_decompress_ptr cinfo)
76 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
78 /* Mark the conversion buffer empty */
79 upsample->next_row_out = cinfo->max_v_samp_factor;
80 /* Initialize total-height counter for detecting bottom of image */
81 upsample->rows_to_go = cinfo->output_height;
86 * Control routine to do upsampling (and color conversion).
88 * In this version we upsample each component independently.
89 * We upsample one row group into the conversion buffer, then apply
90 * color conversion a row at a time.
94 sep_upsample (j_decompress_ptr cinfo,
95 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
96 JDIMENSION in_row_groups_avail,
97 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
98 JDIMENSION out_rows_avail)
100 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
102 jpeg_component_info * compptr;
105 /* Fill the conversion buffer, if it's empty */
106 if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
107 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
109 /* Invoke per-component upsample method. Notice we pass a POINTER
110 * to color_buf[ci], so that fullsize_upsample can change it.
112 (*upsample->methods[ci]) (cinfo, compptr,
113 input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
114 upsample->color_buf + ci);
116 upsample->next_row_out = 0;
119 /* Color-convert and emit rows */
121 /* How many we have in the buffer: */
122 num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
123 /* Not more than the distance to the end of the image. Need this test
124 * in case the image height is not a multiple of max_v_samp_factor:
126 if (num_rows > upsample->rows_to_go)
127 num_rows = upsample->rows_to_go;
128 /* And not more than what the client can accept: */
129 out_rows_avail -= *out_row_ctr;
130 if (num_rows > out_rows_avail)
131 num_rows = out_rows_avail;
133 (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
134 (JDIMENSION) upsample->next_row_out,
135 output_buf + *out_row_ctr,
139 *out_row_ctr += num_rows;
140 upsample->rows_to_go -= num_rows;
141 upsample->next_row_out += num_rows;
142 /* When the buffer is emptied, declare this input row group consumed */
143 if (upsample->next_row_out >= cinfo->max_v_samp_factor)
144 (*in_row_group_ctr)++;
149 * These are the routines invoked by sep_upsample to upsample pixel values
150 * of a single component. One row group is processed per call.
155 * For full-size components, we just make color_buf[ci] point at the
156 * input buffer, and thus avoid copying any data. Note that this is
157 * safe only because sep_upsample doesn't declare the input row group
158 * "consumed" until we are done color converting and emitting it.
162 fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
163 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
165 *output_data_ptr = input_data;
170 * This is a no-op version used for "uninteresting" components.
171 * These components will not be referenced by color conversion.
175 noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
176 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
178 *output_data_ptr = NULL; /* safety check */
183 * This version handles any integral sampling ratios.
184 * This is not used for typical JPEG files, so it need not be fast.
185 * Nor, for that matter, is it particularly accurate: the algorithm is
186 * simple replication of the input pixel onto the corresponding output
187 * pixels. The hi-falutin sampling literature refers to this as a
188 * "box filter". A box filter tends to introduce visible artifacts,
189 * so if you are actually going to use 3:1 or 4:1 sampling ratios
190 * you would be well advised to improve this code.
194 int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
195 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
197 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
198 JSAMPARRAY output_data = *output_data_ptr;
199 register JSAMPROW inptr, outptr;
200 register JSAMPLE invalue;
203 int h_expand, v_expand;
206 h_expand = upsample->h_expand[compptr->component_index];
207 v_expand = upsample->v_expand[compptr->component_index];
210 while (outrow < cinfo->max_v_samp_factor) {
211 /* Generate one output row with proper horizontal expansion */
212 inptr = input_data[inrow];
213 outptr = output_data[outrow];
214 outend = outptr + cinfo->output_width;
215 while (outptr < outend) {
216 invalue = *inptr++; /* don't need GETJSAMPLE() here */
217 for (h = h_expand; h > 0; h--) {
221 /* Generate any additional output rows by duplicating the first one */
223 jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
224 v_expand-1, cinfo->output_width);
233 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
234 * It's still a box filter.
238 h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
239 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
241 JSAMPARRAY output_data = *output_data_ptr;
242 register JSAMPROW inptr, outptr;
243 register JSAMPLE invalue;
247 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
248 inptr = input_data[inrow];
249 outptr = output_data[inrow];
250 outend = outptr + cinfo->output_width;
251 while (outptr < outend) {
252 invalue = *inptr++; /* don't need GETJSAMPLE() here */
261 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
262 * It's still a box filter.
266 h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
267 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
269 JSAMPARRAY output_data = *output_data_ptr;
270 register JSAMPROW inptr, outptr;
271 register JSAMPLE invalue;
276 while (outrow < cinfo->max_v_samp_factor) {
277 inptr = input_data[inrow];
278 outptr = output_data[outrow];
279 outend = outptr + cinfo->output_width;
280 while (outptr < outend) {
281 invalue = *inptr++; /* don't need GETJSAMPLE() here */
285 jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
286 1, cinfo->output_width);
294 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
296 * The upsampling algorithm is linear interpolation between pixel centers,
297 * also known as a "triangle filter". This is a good compromise between
298 * speed and visual quality. The centers of the output pixels are 1/4 and 3/4
299 * of the way between input pixel centers.
301 * A note about the "bias" calculations: when rounding fractional values to
302 * integer, we do not want to always round 0.5 up to the next integer.
303 * If we did that, we'd introduce a noticeable bias towards larger values.
304 * Instead, this code is arranged so that 0.5 will be rounded up or down at
305 * alternate pixel locations (a simple ordered dither pattern).
309 h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
310 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
312 JSAMPARRAY output_data = *output_data_ptr;
313 register JSAMPROW inptr, outptr;
314 register int invalue;
315 register JDIMENSION colctr;
318 for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
319 inptr = input_data[inrow];
320 outptr = output_data[inrow];
321 /* Special case for first column */
322 invalue = GETJSAMPLE(*inptr++);
323 *outptr++ = (JSAMPLE) invalue;
324 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
326 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
327 /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
328 invalue = GETJSAMPLE(*inptr++) * 3;
329 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
330 *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
333 /* Special case for last column */
334 invalue = GETJSAMPLE(*inptr);
335 *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
336 *outptr++ = (JSAMPLE) invalue;
342 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
343 * Again a triangle filter; see comments for h2v1 case, above.
345 * It is OK for us to reference the adjacent input rows because we demanded
346 * context from the main buffer controller (see initialization code).
350 h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
351 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
353 JSAMPARRAY output_data = *output_data_ptr;
354 register JSAMPROW inptr0, inptr1, outptr;
355 #if BITS_IN_JSAMPLE == 8
356 register int thiscolsum, lastcolsum, nextcolsum;
358 register INT32 thiscolsum, lastcolsum, nextcolsum;
360 register JDIMENSION colctr;
361 int inrow, outrow, v;
364 while (outrow < cinfo->max_v_samp_factor) {
365 for (v = 0; v < 2; v++) {
366 /* inptr0 points to nearest input row, inptr1 points to next nearest */
367 inptr0 = input_data[inrow];
368 if (v == 0) /* next nearest is row above */
369 inptr1 = input_data[inrow-1];
370 else /* next nearest is row below */
371 inptr1 = input_data[inrow+1];
372 outptr = output_data[outrow++];
374 /* Special case for first column */
375 thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
376 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
377 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
378 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
379 lastcolsum = thiscolsum; thiscolsum = nextcolsum;
381 for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
382 /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
383 /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
384 nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
385 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
386 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
387 lastcolsum = thiscolsum; thiscolsum = nextcolsum;
390 /* Special case for last column */
391 *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
392 *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
400 * Module initialization routine for upsampling.
404 jinit_upsampler (j_decompress_ptr cinfo)
406 my_upsample_ptr upsample;
408 jpeg_component_info * compptr;
409 boolean need_buffer, do_fancy;
410 int h_in_group, v_in_group, h_out_group, v_out_group;
412 upsample = (my_upsample_ptr)
413 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
414 SIZEOF(my_upsampler));
415 cinfo->upsample = (struct jpeg_upsampler *) upsample;
416 upsample->pub.start_pass = start_pass_upsample;
417 upsample->pub.upsample = sep_upsample;
418 upsample->pub.need_context_rows = FALSE; /* until we find out differently */
420 if (cinfo->CCIR601_sampling) /* this isn't supported */
421 ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
423 /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
424 * so don't ask for it.
426 do_fancy = cinfo->do_fancy_upsampling && cinfo->_min_DCT_scaled_size > 1;
428 /* Verify we can handle the sampling factors, select per-component methods,
429 * and create storage as needed.
431 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
433 /* Compute size of an "input group" after IDCT scaling. This many samples
434 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
436 h_in_group = (compptr->h_samp_factor * compptr->_DCT_scaled_size) /
437 cinfo->_min_DCT_scaled_size;
438 v_in_group = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
439 cinfo->_min_DCT_scaled_size;
440 h_out_group = cinfo->max_h_samp_factor;
441 v_out_group = cinfo->max_v_samp_factor;
442 upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
444 if (! compptr->component_needed) {
445 /* Don't bother to upsample an uninteresting component. */
446 upsample->methods[ci] = noop_upsample;
448 } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
449 /* Fullsize components can be processed without any work. */
450 upsample->methods[ci] = fullsize_upsample;
452 } else if (h_in_group * 2 == h_out_group &&
453 v_in_group == v_out_group) {
454 /* Special cases for 2h1v upsampling */
455 if (do_fancy && compptr->downsampled_width > 2) {
456 if (jsimd_can_h2v1_fancy_upsample())
457 upsample->methods[ci] = jsimd_h2v1_fancy_upsample;
459 upsample->methods[ci] = h2v1_fancy_upsample;
461 if (jsimd_can_h2v1_upsample())
462 upsample->methods[ci] = jsimd_h2v1_upsample;
464 upsample->methods[ci] = h2v1_upsample;
466 } else if (h_in_group * 2 == h_out_group &&
467 v_in_group * 2 == v_out_group) {
468 /* Special cases for 2h2v upsampling */
469 if (do_fancy && compptr->downsampled_width > 2) {
470 if (jsimd_can_h2v2_fancy_upsample())
471 upsample->methods[ci] = jsimd_h2v2_fancy_upsample;
473 upsample->methods[ci] = h2v2_fancy_upsample;
474 upsample->pub.need_context_rows = TRUE;
476 if (jsimd_can_h2v2_upsample())
477 upsample->methods[ci] = jsimd_h2v2_upsample;
479 upsample->methods[ci] = h2v2_upsample;
481 } else if ((h_out_group % h_in_group) == 0 &&
482 (v_out_group % v_in_group) == 0) {
483 /* Generic integral-factors upsampling method */
484 upsample->methods[ci] = int_upsample;
485 upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
486 upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
488 ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
490 upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
491 ((j_common_ptr) cinfo, JPOOL_IMAGE,
492 (JDIMENSION) jround_up((long) cinfo->output_width,
493 (long) cinfo->max_h_samp_factor),
494 (JDIMENSION) cinfo->max_v_samp_factor);