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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)
start_pass_upsample(j_decompress_ptr cinfo)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)
sep_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)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)
fullsize_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
noop_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
int_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
h2v1_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
h2v2_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
h2v1_fancy_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
h2v2_fancy_upsample(j_decompress_ptr cinfo,jpeg_component_info * compptr,JSAMPARRAY input_data,JSAMPARRAY * output_data_ptr)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)
jinit_upsampler(j_decompress_ptr cinfo)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 }
479