MagickCore 7.1.1
Convert, Edit, Or Compose Bitmap Images
Loading...
Searching...
No Matches
resample.c
1/*
2%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3% %
4% %
5% %
6% RRRR EEEEE SSSSS AAA M M PPPP L EEEEE %
7% R R E SS A A MM MM P P L E %
8% RRRR EEE SSS AAAAA M M M PPPP L EEE %
9% R R E SS A A M M P L E %
10% R R EEEEE SSSSS A A M M P LLLLL EEEEE %
11% %
12% %
13% MagickCore Pixel Resampling Methods %
14% %
15% Software Design %
16% Cristy %
17% Anthony Thyssen %
18% August 2007 %
19% %
20% %
21% Copyright @ 1999 ImageMagick Studio LLC, a non-profit organization %
22% dedicated to making software imaging solutions freely available. %
23% %
24% You may not use this file except in compliance with the License. You may %
25% obtain a copy of the License at %
26% %
27% https://imagemagick.org/script/license.php %
28% %
29% Unless required by applicable law or agreed to in writing, software %
30% distributed under the License is distributed on an "AS IS" BASIS, %
31% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. %
32% See the License for the specific language governing permissions and %
33% limitations under the License. %
34% %
35%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36%
37%
38*/
39
40/*
41 Include declarations.
42*/
43#include "MagickCore/studio.h"
44#include "MagickCore/artifact.h"
45#include "MagickCore/color-private.h"
46#include "MagickCore/cache.h"
47#include "MagickCore/draw.h"
48#include "MagickCore/exception-private.h"
49#include "MagickCore/gem.h"
50#include "MagickCore/image.h"
51#include "MagickCore/image-private.h"
52#include "MagickCore/log.h"
53#include "MagickCore/magick.h"
54#include "MagickCore/memory_.h"
55#include "MagickCore/memory-private.h"
56#include "MagickCore/pixel.h"
57#include "MagickCore/pixel-accessor.h"
58#include "MagickCore/quantum.h"
59#include "MagickCore/random_.h"
60#include "MagickCore/resample.h"
61#include "MagickCore/resize.h"
62#include "MagickCore/resize-private.h"
63#include "MagickCore/resource_.h"
64#include "MagickCore/token.h"
65#include "MagickCore/transform.h"
66#include "MagickCore/signature-private.h"
67#include "MagickCore/utility.h"
68#include "MagickCore/utility-private.h"
69#include "MagickCore/option.h"
70/*
71 EWA Resampling Options
72*/
73
74/* select ONE resampling method */
75#define EWA 1 /* Normal EWA handling - raw or clamped */
76 /* if 0 then use "High Quality EWA" */
77#define EWA_CLAMP 1 /* EWA Clamping from Nicolas Robidoux */
78
79#define FILTER_LUT 1 /* Use a LUT rather then direct filter calls */
80
81/* output debugging information */
82#define DEBUG_ELLIPSE 0 /* output ellipse info for debug */
83#define DEBUG_HIT_MISS 0 /* output hit/miss pixels (as gnuplot commands) */
84#define DEBUG_NO_PIXEL_HIT 0 /* Make pixels that fail to hit anything - RED */
85
86#if ! FILTER_DIRECT
87#define WLUT_WIDTH 1024 /* size of the filter cache */
88#endif
89
90/*
91 Typedef declarations.
92*/
94{
96 *view;
97
98 Image
99 *image;
100
102 *exception;
103
104 MagickBooleanType
105 debug;
106
107 /* Information about image being resampled */
108 ssize_t
109 image_area;
110
111 PixelInterpolateMethod
112 interpolate;
113
114 VirtualPixelMethod
115 virtual_pixel;
116
117 FilterType
118 filter;
119
120 /* processing settings needed */
121 MagickBooleanType
122 limit_reached,
123 do_interpolate,
124 average_defined;
125
127 average_pixel;
128
129 /* current elliptical area being resampled around center point */
130 double
131 A, B, C,
132 Vlimit, Ulimit, Uwidth, slope;
133
134#if FILTER_LUT
135 /* LUT of weights for filtered average in elliptical area */
136 double
137 filter_lut[WLUT_WIDTH];
138#else
139 /* Use a Direct call to the filter functions */
141 *filter_def;
142
143 double
144 F;
145#endif
146
147 /* the practical working support of the filter */
148 double
149 support;
150
151 size_t
152 signature;
153};
154
155/*
156%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
157% %
158% %
159% %
160% A c q u i r e R e s a m p l e I n f o %
161% %
162% %
163% %
164%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
165%
166% AcquireResampleFilter() initializes the information resample needs do to a
167% scaled lookup of a color from an image, using area sampling.
168%
169% The algorithm is based on a Elliptical Weighted Average, where the pixels
170% found in a large elliptical area is averaged together according to a
171% weighting (filter) function. For more details see "Fundamentals of Texture
172% Mapping and Image Warping" a master's thesis by Paul.S.Heckbert, June 17,
173% 1989. Available for free from, http://www.cs.cmu.edu/~ph/
174%
175% As EWA resampling (or any sort of resampling) can require a lot of
176% calculations to produce a distorted scaling of the source image for each
177% output pixel, the ResampleFilter structure generated holds that information
178% between individual image resampling.
179%
180% This function will make the appropriate AcquireCacheView() calls
181% to view the image, calling functions do not need to open a cache view.
182%
183% Usage Example...
184% resample_filter=AcquireResampleFilter(image,exception);
185% SetResampleFilter(resample_filter, GaussianFilter);
186% for (y=0; y < (ssize_t) image->rows; y++) {
187% for (x=0; x < (ssize_t) image->columns; x++) {
188% u= ....; v= ....;
189% ScaleResampleFilter(resample_filter, ... scaling vectors ...);
190% (void) ResamplePixelColor(resample_filter,u,v,&pixel);
191% ... assign resampled pixel value ...
192% }
193% }
194% DestroyResampleFilter(resample_filter);
195%
196% The format of the AcquireResampleFilter method is:
197%
198% ResampleFilter *AcquireResampleFilter(const Image *image,
199% ExceptionInfo *exception)
200%
201% A description of each parameter follows:
202%
203% o image: the image.
204%
205% o exception: return any errors or warnings in this structure.
206%
207*/
208MagickExport ResampleFilter *AcquireResampleFilter(const Image *image,
209 ExceptionInfo *exception)
210{
212 *resample_filter;
213
214 assert(image != (Image *) NULL);
215 assert(image->signature == MagickCoreSignature);
216 assert(exception != (ExceptionInfo *) NULL);
217 assert(exception->signature == MagickCoreSignature);
218 if (IsEventLogging() != MagickFalse)
219 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
220 resample_filter=(ResampleFilter *) AcquireCriticalMemory(sizeof(
221 *resample_filter));
222 (void) memset(resample_filter,0,sizeof(*resample_filter));
223 resample_filter->exception=exception;
224 resample_filter->image=ReferenceImage((Image *) image);
225 resample_filter->view=AcquireVirtualCacheView(resample_filter->image,
226 exception);
227 resample_filter->debug=IsEventLogging();
228 resample_filter->image_area=(ssize_t) (image->columns*image->rows);
229 resample_filter->average_defined=MagickFalse;
230 resample_filter->signature=MagickCoreSignature;
231 SetResampleFilter(resample_filter,image->filter);
232 (void) SetResampleFilterInterpolateMethod(resample_filter,image->interpolate);
233 (void) SetResampleFilterVirtualPixelMethod(resample_filter,
234 GetImageVirtualPixelMethod(image));
235 return(resample_filter);
236}
237
238/*
239%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
240% %
241% %
242% %
243% D e s t r o y R e s a m p l e I n f o %
244% %
245% %
246% %
247%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
248%
249% DestroyResampleFilter() finalizes and cleans up the resampling
250% resample_filter as returned by AcquireResampleFilter(), freeing any memory
251% or other information as needed.
252%
253% The format of the DestroyResampleFilter method is:
254%
255% ResampleFilter *DestroyResampleFilter(ResampleFilter *resample_filter)
256%
257% A description of each parameter follows:
258%
259% o resample_filter: resampling information structure
260%
261*/
262MagickExport ResampleFilter *DestroyResampleFilter(
263 ResampleFilter *resample_filter)
264{
265 assert(resample_filter != (ResampleFilter *) NULL);
266 assert(resample_filter->signature == MagickCoreSignature);
267 assert(resample_filter->image != (Image *) NULL);
268 if (IsEventLogging() != MagickFalse)
269 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
270 resample_filter->image->filename);
271 resample_filter->view=DestroyCacheView(resample_filter->view);
272 resample_filter->image=DestroyImage(resample_filter->image);
273#if ! FILTER_LUT
274 resample_filter->filter_def=DestroyResizeFilter(resample_filter->filter_def);
275#endif
276 resample_filter->signature=(~MagickCoreSignature);
277 resample_filter=(ResampleFilter *) RelinquishMagickMemory(resample_filter);
278 return(resample_filter);
279}
280
281/*
282%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
283% %
284% %
285% %
286% R e s a m p l e P i x e l C o l o r %
287% %
288% %
289% %
290%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
291%
292% ResamplePixelColor() samples the pixel values surrounding the location
293% given using an elliptical weighted average, at the scale previously
294% calculated, and in the most efficient manner possible for the
295% VirtualPixelMethod setting.
296%
297% The format of the ResamplePixelColor method is:
298%
299% MagickBooleanType ResamplePixelColor(ResampleFilter *resample_filter,
300% const double u0,const double v0,PixelInfo *pixel,
301% ExceptionInfo *exception)
302%
303% A description of each parameter follows:
304%
305% o resample_filter: the resample filter.
306%
307% o u0,v0: A double representing the center of the area to resample,
308% The distortion transformed x,y coordinate.
309%
310% o pixel: the resampled pixel is returned here.
311%
312% o exception: return any errors or warnings in this structure.
313%
314*/
315MagickExport MagickBooleanType ResamplePixelColor(
316 ResampleFilter *resample_filter,const double u0,const double v0,
317 PixelInfo *pixel,ExceptionInfo *exception)
318{
319 MagickBooleanType
320 status;
321
322 ssize_t u,v, v1, v2, uw, hit;
323 double u1;
324 double U,V,Q,DQ,DDQ;
325 double divisor_c,divisor_m;
326 double weight;
327 const Quantum *pixels;
328 assert(resample_filter != (ResampleFilter *) NULL);
329 assert(resample_filter->signature == MagickCoreSignature);
330
331 status=MagickTrue;
332 /* GetPixelInfo(resample_filter->image,pixel); */
333 if ( resample_filter->do_interpolate ) {
334 status=InterpolatePixelInfo(resample_filter->image,resample_filter->view,
335 resample_filter->interpolate,u0,v0,pixel,resample_filter->exception);
336 return(status);
337 }
338
339#if DEBUG_ELLIPSE
340 (void) FormatLocaleFile(stderr, "u0=%lf; v0=%lf;\n", u0, v0);
341#endif
342
343 /*
344 Does resample area Miss the image Proper?
345 If and that area a simple solid color - then simply return that color!
346 This saves a lot of calculation when resampling outside the bounds of
347 the source image.
348
349 However it probably should be expanded to image bounds plus the filters
350 scaled support size.
351 */
352 hit = 0;
353 switch ( resample_filter->virtual_pixel ) {
354 case BackgroundVirtualPixelMethod:
355 case TransparentVirtualPixelMethod:
356 case BlackVirtualPixelMethod:
357 case GrayVirtualPixelMethod:
358 case WhiteVirtualPixelMethod:
359 case MaskVirtualPixelMethod:
360 if ( resample_filter->limit_reached
361 || u0 + resample_filter->Ulimit < 0.0
362 || u0 - resample_filter->Ulimit > (double) resample_filter->image->columns-1.0
363 || v0 + resample_filter->Vlimit < 0.0
364 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows-1.0
365 )
366 hit++;
367 break;
368
369 case UndefinedVirtualPixelMethod:
370 case EdgeVirtualPixelMethod:
371 if ( ( u0 + resample_filter->Ulimit < 0.0 && v0 + resample_filter->Vlimit < 0.0 )
372 || ( u0 + resample_filter->Ulimit < 0.0
373 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows-1.0 )
374 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns-1.0
375 && v0 + resample_filter->Vlimit < 0.0 )
376 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns-1.0
377 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows-1.0 )
378 )
379 hit++;
380 break;
381 case HorizontalTileVirtualPixelMethod:
382 if ( v0 + resample_filter->Vlimit < 0.0
383 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows-1.0
384 )
385 hit++; /* outside the horizontally tiled images. */
386 break;
387 case VerticalTileVirtualPixelMethod:
388 if ( u0 + resample_filter->Ulimit < 0.0
389 || u0 - resample_filter->Ulimit > (double) resample_filter->image->columns-1.0
390 )
391 hit++; /* outside the vertically tiled images. */
392 break;
393 case DitherVirtualPixelMethod:
394 if ( ( u0 + resample_filter->Ulimit < -32.0 && v0 + resample_filter->Vlimit < -32.0 )
395 || ( u0 + resample_filter->Ulimit < -32.0
396 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows+31.0 )
397 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+31.0
398 && v0 + resample_filter->Vlimit < -32.0 )
399 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+31.0
400 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows+31.0 )
401 )
402 hit++;
403 break;
404 case TileVirtualPixelMethod:
405 case MirrorVirtualPixelMethod:
406 case RandomVirtualPixelMethod:
407 case HorizontalTileEdgeVirtualPixelMethod:
408 case VerticalTileEdgeVirtualPixelMethod:
409 case CheckerTileVirtualPixelMethod:
410 /* resampling of area is always needed - no VP limits */
411 break;
412 }
413 if ( hit ) {
414 /* The area being resampled is simply a solid color
415 * just return a single lookup color.
416 *
417 * Should this return the users requested interpolated color?
418 */
419 status=InterpolatePixelInfo(resample_filter->image,resample_filter->view,
420 IntegerInterpolatePixel,u0,v0,pixel,resample_filter->exception);
421 return(status);
422 }
423
424 /*
425 When Scaling limits reached, return an 'averaged' result.
426 */
427 if ( resample_filter->limit_reached ) {
428 switch ( resample_filter->virtual_pixel ) {
429 /* This is always handled by the above, so no need.
430 case BackgroundVirtualPixelMethod:
431 case ConstantVirtualPixelMethod:
432 case TransparentVirtualPixelMethod:
433 case GrayVirtualPixelMethod,
434 case WhiteVirtualPixelMethod
435 case MaskVirtualPixelMethod:
436 */
437 case UndefinedVirtualPixelMethod:
438 case EdgeVirtualPixelMethod:
439 case DitherVirtualPixelMethod:
440 case HorizontalTileEdgeVirtualPixelMethod:
441 case VerticalTileEdgeVirtualPixelMethod:
442 /* We need an average edge pixel, from the correct edge!
443 How should I calculate an average edge color?
444 Just returning an averaged neighbourhood,
445 works well in general, but falls down for TileEdge methods.
446 This needs to be done properly!!!!!!
447 */
448 status=InterpolatePixelInfo(resample_filter->image,
449 resample_filter->view,AverageInterpolatePixel,u0,v0,pixel,
450 resample_filter->exception);
451 break;
452 case HorizontalTileVirtualPixelMethod:
453 case VerticalTileVirtualPixelMethod:
454 /* just return the background pixel - Is there more direct way? */
455 status=InterpolatePixelInfo(resample_filter->image,
456 resample_filter->view,IntegerInterpolatePixel,-1.0,-1.0,pixel,
457 resample_filter->exception);
458 break;
459 case TileVirtualPixelMethod:
460 case MirrorVirtualPixelMethod:
461 case RandomVirtualPixelMethod:
462 case CheckerTileVirtualPixelMethod:
463 default:
464 /* generate a average color of the WHOLE image */
465 if ( resample_filter->average_defined == MagickFalse ) {
466 Image
467 *average_image;
468
470 *average_view;
471
472 GetPixelInfo(resample_filter->image,(PixelInfo *)
473 &resample_filter->average_pixel);
474 resample_filter->average_defined=MagickTrue;
475
476 /* Try to get an averaged pixel color of whole image */
477 average_image=ResizeImage(resample_filter->image,1,1,BoxFilter,
478 resample_filter->exception);
479 if (average_image == (Image *) NULL)
480 {
481 *pixel=resample_filter->average_pixel; /* FAILED */
482 break;
483 }
484 average_view=AcquireVirtualCacheView(average_image,exception);
485 pixels=GetCacheViewVirtualPixels(average_view,0,0,1,1,
486 resample_filter->exception);
487 if (pixels == (const Quantum *) NULL) {
488 average_view=DestroyCacheView(average_view);
489 average_image=DestroyImage(average_image);
490 *pixel=resample_filter->average_pixel; /* FAILED */
491 break;
492 }
493 GetPixelInfoPixel(resample_filter->image,pixels,
494 &(resample_filter->average_pixel));
495 average_view=DestroyCacheView(average_view);
496 average_image=DestroyImage(average_image);
497
498 if ( resample_filter->virtual_pixel == CheckerTileVirtualPixelMethod )
499 {
500 /* CheckerTile is a alpha blend of the image's average pixel
501 color and the current background color */
502
503 /* image's average pixel color */
504 weight = QuantumScale*((double)
505 resample_filter->average_pixel.alpha);
506 resample_filter->average_pixel.red *= weight;
507 resample_filter->average_pixel.green *= weight;
508 resample_filter->average_pixel.blue *= weight;
509 divisor_c = weight;
510
511 /* background color */
512 weight = QuantumScale*((double)
513 resample_filter->image->background_color.alpha);
514 resample_filter->average_pixel.red +=
515 weight*resample_filter->image->background_color.red;
516 resample_filter->average_pixel.green +=
517 weight*resample_filter->image->background_color.green;
518 resample_filter->average_pixel.blue +=
519 weight*resample_filter->image->background_color.blue;
520 resample_filter->average_pixel.alpha +=
521 resample_filter->image->background_color.alpha;
522 divisor_c += weight;
523
524 /* alpha blend */
525 resample_filter->average_pixel.red /= divisor_c;
526 resample_filter->average_pixel.green /= divisor_c;
527 resample_filter->average_pixel.blue /= divisor_c;
528 resample_filter->average_pixel.alpha /= 2; /* 50% blend */
529
530 }
531 }
532 *pixel=resample_filter->average_pixel;
533 break;
534 }
535 return(status);
536 }
537
538 /*
539 Initialize weighted average data collection
540 */
541 hit = 0;
542 divisor_c = 0.0;
543 divisor_m = 0.0;
544 pixel->red = pixel->green = pixel->blue = 0.0;
545 if (pixel->colorspace == CMYKColorspace)
546 pixel->black = 0.0;
547 if (pixel->alpha_trait != UndefinedPixelTrait)
548 pixel->alpha = 0.0;
549
550 /*
551 Determine the parallelogram bounding box fitted to the ellipse
552 centered at u0,v0. This area is bounding by the lines...
553 */
554 v1 = (ssize_t)ceil(v0 - resample_filter->Vlimit); /* range of scan lines */
555 v2 = (ssize_t)floor(v0 + resample_filter->Vlimit);
556
557 /* scan line start and width across the parallelogram */
558 u1 = u0 + (v1-v0)*resample_filter->slope - resample_filter->Uwidth;
559 uw = (ssize_t)(2.0*resample_filter->Uwidth)+1;
560
561#if DEBUG_ELLIPSE
562 (void) FormatLocaleFile(stderr, "v1=%ld; v2=%ld\n", (long)v1, (long)v2);
563 (void) FormatLocaleFile(stderr, "u1=%ld; uw=%ld\n", (long)u1, (long)uw);
564#else
565# define DEBUG_HIT_MISS 0 /* only valid if DEBUG_ELLIPSE is enabled */
566#endif
567
568 /*
569 Do weighted resampling of all pixels, within the scaled ellipse,
570 bound by a Parallelogram fitted to the ellipse.
571 */
572 DDQ = 2*resample_filter->A;
573 for( v=v1; v<=v2; v++ ) {
574#if DEBUG_HIT_MISS
575 long uu = ceil(u1); /* actual pixel location (for debug only) */
576 (void) FormatLocaleFile(stderr, "# scan line from pixel %ld, %ld\n", (long)uu, (long)v);
577#endif
578 u = (ssize_t)ceil(u1); /* first pixel in scanline */
579 u1 += resample_filter->slope; /* start of next scan line */
580
581
582 /* location of this first pixel, relative to u0,v0 */
583 U = (double)u-u0;
584 V = (double)v-v0;
585
586 /* Q = ellipse quotient ( if Q<F then pixel is inside ellipse) */
587 Q = (resample_filter->A*U + resample_filter->B*V)*U + resample_filter->C*V*V;
588 DQ = resample_filter->A*(2.0*U+1) + resample_filter->B*V;
589
590 /* get the scanline of pixels for this v */
591 pixels=GetCacheViewVirtualPixels(resample_filter->view,u,v,(size_t) uw,
592 1,resample_filter->exception);
593 if (pixels == (const Quantum *) NULL)
594 return(MagickFalse);
595
596 /* count up the weighted pixel colors */
597 for( u=0; u<uw; u++ ) {
598 weight = 0.0;
599#if FILTER_LUT
600 /* Note that the ellipse has been pre-scaled so F = WLUT_WIDTH */
601 if ((Q >= 0.0) && ((int) Q < WLUT_WIDTH)) {
602 weight = resample_filter->filter_lut[(int)Q];
603#else
604 /* Note that the ellipse has been pre-scaled so F = support^2 */
605 if ((Q >= 0.0) && (Q < (double)resample_filter->F)) {
606 weight = GetResizeFilterWeight(resample_filter->filter_def,
607 sqrt(Q)); /* a SquareRoot! Arrggghhhhh... */
608#endif
609
610 pixel->alpha+=weight*(double)
611 GetPixelAlpha(resample_filter->image,pixels);
612 divisor_m += weight;
613
614 if (pixel->alpha_trait != UndefinedPixelTrait)
615 weight*=QuantumScale*((double)
616 GetPixelAlpha(resample_filter->image,pixels));
617 pixel->red+=weight*(double)
618 GetPixelRed(resample_filter->image,pixels);
619 pixel->green+=weight*(double)
620 GetPixelGreen(resample_filter->image,pixels);
621 pixel->blue+=weight*(double)
622 GetPixelBlue(resample_filter->image,pixels);
623 if (pixel->colorspace == CMYKColorspace)
624 pixel->black+=weight*(double)
625 GetPixelBlack(resample_filter->image,pixels);
626 divisor_c += weight;
627
628 hit++;
629#if DEBUG_HIT_MISS
630 /* mark the pixel according to hit/miss of the ellipse */
631 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
632 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
633 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
634 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
635 } else {
636 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
637 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
638 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
639 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
640 }
641 uu++;
642#else
643 }
644#endif
645 pixels+=GetPixelChannels(resample_filter->image);
646 Q += DQ;
647 DQ += DDQ;
648 }
649 }
650#if DEBUG_ELLIPSE
651 (void) FormatLocaleFile(stderr, "Hit=%ld; Total=%ld;\n", (long)hit, (long)uw*(v2-v1) );
652#endif
653
654 /*
655 Result sanity check -- this should NOT happen
656 */
657 if ( hit == 0 || divisor_m <= MagickEpsilon || divisor_c <= MagickEpsilon ) {
658 /* not enough pixels, or bad weighting in resampling,
659 resort to direct interpolation */
660#if DEBUG_NO_PIXEL_HIT
661 pixel->alpha = pixel->red = pixel->green = pixel->blue = 0;
662 pixel->red = QuantumRange; /* show pixels for which EWA fails */
663#else
664 status=InterpolatePixelInfo(resample_filter->image,
665 resample_filter->view,resample_filter->interpolate,u0,v0,pixel,
666 resample_filter->exception);
667#endif
668 return status;
669 }
670
671 /*
672 Finalize results of resampling
673 */
674 divisor_m = 1.0/divisor_m;
675 if (pixel->alpha_trait != UndefinedPixelTrait)
676 pixel->alpha = (double) ClampToQuantum(divisor_m*pixel->alpha);
677 divisor_c = 1.0/divisor_c;
678 pixel->red = (double) ClampToQuantum(divisor_c*pixel->red);
679 pixel->green = (double) ClampToQuantum(divisor_c*pixel->green);
680 pixel->blue = (double) ClampToQuantum(divisor_c*pixel->blue);
681 if (pixel->colorspace == CMYKColorspace)
682 pixel->black = (double) ClampToQuantum(divisor_c*pixel->black);
683 return(MagickTrue);
684}
685
686#if EWA && EWA_CLAMP
687/*
688%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
689% %
690% %
691% %
692- C l a m p U p A x e s %
693% %
694% %
695% %
696%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
697%
698% ClampUpAxes() function converts the input vectors into a major and
699% minor axis unit vectors, and their magnitude. This allows us to
700% ensure that the ellipse generated is never smaller than the unit
701% circle and thus never too small for use in EWA resampling.
702%
703% This purely mathematical 'magic' was provided by Professor Nicolas
704% Robidoux and his Masters student Chantal Racette.
705%
706% Reference: "We Recommend Singular Value Decomposition", David Austin
707% http://www.ams.org/samplings/feature-column/fcarc-svd
708%
709% By generating major and minor axis vectors, we can actually use the
710% ellipse in its "canonical form", by remapping the dx,dy of the
711% sampled point into distances along the major and minor axis unit
712% vectors.
713%
714% Reference: http://en.wikipedia.org/wiki/Ellipse#Canonical_form
715*/
716static inline void ClampUpAxes(const double dux,
717 const double dvx,
718 const double duy,
719 const double dvy,
720 double *major_mag,
721 double *minor_mag,
722 double *major_unit_x,
723 double *major_unit_y,
724 double *minor_unit_x,
725 double *minor_unit_y)
726{
727 /*
728 * ClampUpAxes takes an input 2x2 matrix
729 *
730 * [ a b ] = [ dux duy ]
731 * [ c d ] = [ dvx dvy ]
732 *
733 * and computes from it the major and minor axis vectors [major_x,
734 * major_y] and [minor_x,minor_y] of the smallest ellipse containing
735 * both the unit disk and the ellipse which is the image of the unit
736 * disk by the linear transformation
737 *
738 * [ dux duy ] [S] = [s]
739 * [ dvx dvy ] [T] = [t]
740 *
741 * (The vector [S,T] is the difference between a position in output
742 * space and [X,Y]; the vector [s,t] is the difference between a
743 * position in input space and [x,y].)
744 */
745 /*
746 * Output:
747 *
748 * major_mag is the half-length of the major axis of the "new"
749 * ellipse.
750 *
751 * minor_mag is the half-length of the minor axis of the "new"
752 * ellipse.
753 *
754 * major_unit_x is the x-coordinate of the major axis direction vector
755 * of both the "old" and "new" ellipses.
756 *
757 * major_unit_y is the y-coordinate of the major axis direction vector.
758 *
759 * minor_unit_x is the x-coordinate of the minor axis direction vector.
760 *
761 * minor_unit_y is the y-coordinate of the minor axis direction vector.
762 *
763 * Unit vectors are useful for computing projections, in particular,
764 * to compute the distance between a point in output space and the
765 * center of a unit disk in output space, using the position of the
766 * corresponding point [s,t] in input space. Following the clamping,
767 * the square of this distance is
768 *
769 * ( ( s * major_unit_x + t * major_unit_y ) / major_mag )^2
770 * +
771 * ( ( s * minor_unit_x + t * minor_unit_y ) / minor_mag )^2
772 *
773 * If such distances will be computed for many [s,t]'s, it makes
774 * sense to actually compute the reciprocal of major_mag and
775 * minor_mag and multiply them by the above unit lengths.
776 *
777 * Now, if you want to modify the input pair of tangent vectors so
778 * that it defines the modified ellipse, all you have to do is set
779 *
780 * newdux = major_mag * major_unit_x
781 * newdvx = major_mag * major_unit_y
782 * newduy = minor_mag * minor_unit_x = minor_mag * -major_unit_y
783 * newdvy = minor_mag * minor_unit_y = minor_mag * major_unit_x
784 *
785 * and use these tangent vectors as if they were the original ones.
786 * Usually, this is a drastic change in the tangent vectors even if
787 * the singular values are not clamped; for example, the minor axis
788 * vector always points in a direction which is 90 degrees
789 * counterclockwise from the direction of the major axis vector.
790 */
791 /*
792 * Discussion:
793 *
794 * GOAL: Fix things so that the pullback, in input space, of a disk
795 * of radius r in output space is an ellipse which contains, at
796 * least, a disc of radius r. (Make this hold for any r>0.)
797 *
798 * ESSENCE OF THE METHOD: Compute the product of the first two
799 * factors of an SVD of the linear transformation defining the
800 * ellipse and make sure that both its columns have norm at least 1.
801 * Because rotations and reflexions map disks to themselves, it is
802 * not necessary to compute the third (rightmost) factor of the SVD.
803 *
804 * DETAILS: Find the singular values and (unit) left singular
805 * vectors of Jinv, clampling up the singular values to 1, and
806 * multiply the unit left singular vectors by the new singular
807 * values in order to get the minor and major ellipse axis vectors.
808 *
809 * Image resampling context:
810 *
811 * The Jacobian matrix of the transformation at the output point
812 * under consideration is defined as follows:
813 *
814 * Consider the transformation (x,y) -> (X,Y) from input locations
815 * to output locations. (Anthony Thyssen, elsewhere in resample.c,
816 * uses the notation (u,v) -> (x,y).)
817 *
818 * The Jacobian matrix of the transformation at (x,y) is equal to
819 *
820 * J = [ A, B ] = [ dX/dx, dX/dy ]
821 * [ C, D ] [ dY/dx, dY/dy ]
822 *
823 * that is, the vector [A,C] is the tangent vector corresponding to
824 * input changes in the horizontal direction, and the vector [B,D]
825 * is the tangent vector corresponding to input changes in the
826 * vertical direction.
827 *
828 * In the context of resampling, it is natural to use the inverse
829 * Jacobian matrix Jinv because resampling is generally performed by
830 * pulling pixel locations in the output image back to locations in
831 * the input image. Jinv is
832 *
833 * Jinv = [ a, b ] = [ dx/dX, dx/dY ]
834 * [ c, d ] [ dy/dX, dy/dY ]
835 *
836 * Note: Jinv can be computed from J with the following matrix
837 * formula:
838 *
839 * Jinv = 1/(A*D-B*C) [ D, -B ]
840 * [ -C, A ]
841 *
842 * What we do is modify Jinv so that it generates an ellipse which
843 * is as close as possible to the original but which contains the
844 * unit disk. This can be accomplished as follows:
845 *
846 * Let
847 *
848 * Jinv = U Sigma V^T
849 *
850 * be an SVD decomposition of Jinv. (The SVD is not unique, but the
851 * final ellipse does not depend on the particular SVD.)
852 *
853 * We could clamp up the entries of the diagonal matrix Sigma so
854 * that they are at least 1, and then set
855 *
856 * Jinv = U newSigma V^T.
857 *
858 * However, we do not need to compute V for the following reason:
859 * V^T is an orthogonal matrix (that is, it represents a combination
860 * of rotations and reflexions) so that it maps the unit circle to
861 * itself. For this reason, the exact value of V does not affect the
862 * final ellipse, and we can choose V to be the identity
863 * matrix. This gives
864 *
865 * Jinv = U newSigma.
866 *
867 * In the end, we return the two diagonal entries of newSigma
868 * together with the two columns of U.
869 */
870 /*
871 * ClampUpAxes was written by Nicolas Robidoux and Chantal Racette
872 * of Laurentian University with insightful suggestions from Anthony
873 * Thyssen and funding from the National Science and Engineering
874 * Research Council of Canada. It is distinguished from its
875 * predecessors by its efficient handling of degenerate cases.
876 *
877 * The idea of clamping up the EWA ellipse's major and minor axes so
878 * that the result contains the reconstruction kernel filter support
879 * is taken from Andreas Gustafsson's Masters thesis "Interactive
880 * Image Warping", Helsinki University of Technology, Faculty of
881 * Information Technology, 59 pages, 1993 (see Section 3.6).
882 *
883 * The use of the SVD to clamp up the singular values of the
884 * Jacobian matrix of the pullback transformation for EWA resampling
885 * is taken from the astrophysicist Craig DeForest. It is
886 * implemented in his PDL::Transform code (PDL = Perl Data
887 * Language).
888 */
889 const double a = dux;
890 const double b = duy;
891 const double c = dvx;
892 const double d = dvy;
893 /*
894 * n is the matrix Jinv * transpose(Jinv). Eigenvalues of n are the
895 * squares of the singular values of Jinv.
896 */
897 const double aa = a*a;
898 const double bb = b*b;
899 const double cc = c*c;
900 const double dd = d*d;
901 /*
902 * Eigenvectors of n are left singular vectors of Jinv.
903 */
904 const double n11 = aa+bb;
905 const double n12 = a*c+b*d;
906 const double n21 = n12;
907 const double n22 = cc+dd;
908 const double det = a*d-b*c;
909 const double twice_det = det+det;
910 const double frobenius_squared = n11+n22;
911 const double discriminant =
912 (frobenius_squared+twice_det)*(frobenius_squared-twice_det);
913 /*
914 * In exact arithmetic, discriminant can't be negative. In floating
915 * point, it can, because of the bad conditioning of SVD
916 * decompositions done through the associated normal matrix.
917 */
918 const double sqrt_discriminant =
919 sqrt(discriminant > 0.0 ? discriminant : 0.0);
920 /*
921 * s1 is the largest singular value of the inverse Jacobian
922 * matrix. In other words, its reciprocal is the smallest singular
923 * value of the Jacobian matrix itself.
924 * If s1 = 0, both singular values are 0, and any orthogonal pair of
925 * left and right factors produces a singular decomposition of Jinv.
926 */
927 /*
928 * Initially, we only compute the squares of the singular values.
929 */
930 const double s1s1 = 0.5*(frobenius_squared+sqrt_discriminant);
931 /*
932 * s2 the smallest singular value of the inverse Jacobian
933 * matrix. Its reciprocal is the largest singular value of the
934 * Jacobian matrix itself.
935 */
936 const double s2s2 = 0.5*(frobenius_squared-sqrt_discriminant);
937 const double s1s1minusn11 = s1s1-n11;
938 const double s1s1minusn22 = s1s1-n22;
939 /*
940 * u1, the first column of the U factor of a singular decomposition
941 * of Jinv, is a (non-normalized) left singular vector corresponding
942 * to s1. It has entries u11 and u21. We compute u1 from the fact
943 * that it is an eigenvector of n corresponding to the eigenvalue
944 * s1^2.
945 */
946 const double s1s1minusn11_squared = s1s1minusn11*s1s1minusn11;
947 const double s1s1minusn22_squared = s1s1minusn22*s1s1minusn22;
948 /*
949 * The following selects the largest row of n-s1^2 I as the one
950 * which is used to find the eigenvector. If both s1^2-n11 and
951 * s1^2-n22 are zero, n-s1^2 I is the zero matrix. In that case,
952 * any vector is an eigenvector; in addition, norm below is equal to
953 * zero, and, in exact arithmetic, this is the only case in which
954 * norm = 0. So, setting u1 to the simple but arbitrary vector [1,0]
955 * if norm = 0 safely takes care of all cases.
956 */
957 const double temp_u11 =
958 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? n12 : s1s1minusn22 );
959 const double temp_u21 =
960 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? s1s1minusn11 : n21 );
961 const double norm = sqrt(temp_u11*temp_u11+temp_u21*temp_u21);
962 /*
963 * Finalize the entries of first left singular vector (associated
964 * with the largest singular value).
965 */
966 const double u11 = ( (norm>0.0) ? temp_u11/norm : 1.0 );
967 const double u21 = ( (norm>0.0) ? temp_u21/norm : 0.0 );
968 /*
969 * Clamp the singular values up to 1.
970 */
971 *major_mag = ( (s1s1<=1.0) ? 1.0 : sqrt(s1s1) );
972 *minor_mag = ( (s2s2<=1.0) ? 1.0 : sqrt(s2s2) );
973 /*
974 * Return the unit major and minor axis direction vectors.
975 */
976 *major_unit_x = u11;
977 *major_unit_y = u21;
978 *minor_unit_x = -u21;
979 *minor_unit_y = u11;
980}
981
982#endif
983/*
984%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
985% %
986% %
987% %
988% S c a l e R e s a m p l e F i l t e r %
989% %
990% %
991% %
992%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
993%
994% ScaleResampleFilter() does all the calculations needed to resample an image
995% at a specific scale, defined by two scaling vectors. This not using
996% a orthogonal scaling, but two distorted scaling vectors, to allow the
997% generation of a angled ellipse.
998%
999% As only two derivative scaling vectors are used the center of the ellipse
1000% must be the center of the lookup. That is any curvature that the
1001% distortion may produce is discounted.
1002%
1003% The input vectors are produced by either finding the derivatives of the
1004% distortion function, or the partial derivatives from a distortion mapping.
1005% They do not need to be the orthogonal dx,dy scaling vectors, but can be
1006% calculated from other derivatives. For example you could use dr,da/r
1007% polar coordinate vector scaling vectors
1008%
1009% If u,v = DistortEquation(x,y) OR u = Fu(x,y); v = Fv(x,y)
1010% Then the scaling vectors are determined from the derivatives...
1011% du/dx, dv/dx and du/dy, dv/dy
1012% If the resulting scaling vectors is orthogonally aligned then...
1013% dv/dx = 0 and du/dy = 0
1014% Producing an orthogonally aligned ellipse in source space for the area to
1015% be resampled.
1016%
1017% Note that scaling vectors are different to argument order. Argument order
1018% is the general order the derivatives are extracted from the distortion
1019% equations, and not the scaling vectors. As such the middle two values
1020% may be swapped from what you expect. Caution is advised.
1021%
1022% WARNING: It is assumed that any SetResampleFilter() method call will
1023% always be performed before the ScaleResampleFilter() method, so that the
1024% size of the ellipse will match the support for the resampling filter being
1025% used.
1026%
1027% The format of the ScaleResampleFilter method is:
1028%
1029% void ScaleResampleFilter(const ResampleFilter *resample_filter,
1030% const double dux,const double duy,const double dvx,const double dvy)
1031%
1032% A description of each parameter follows:
1033%
1034% o resample_filter: the resampling information defining the
1035% image being resampled
1036%
1037% o dux,duy,dvx,dvy:
1038% The derivatives or scaling vectors defining the EWA ellipse.
1039% NOTE: watch the order, which is based on the order derivatives
1040% are usually determined from distortion equations (see above).
1041% The middle two values may need to be swapped if you are thinking
1042% in terms of scaling vectors.
1043%
1044*/
1045MagickExport void ScaleResampleFilter(ResampleFilter *resample_filter,
1046 const double dux,const double duy,const double dvx,const double dvy)
1047{
1048 double A,B,C,F;
1049
1050 assert(resample_filter != (ResampleFilter *) NULL);
1051 assert(resample_filter->signature == MagickCoreSignature);
1052
1053 resample_filter->limit_reached = MagickFalse;
1054
1055 /* A 'point' filter forces use of interpolation instead of area sampling */
1056 if ( resample_filter->filter == PointFilter )
1057 return; /* EWA turned off - nothing to do */
1058
1059#if DEBUG_ELLIPSE
1060 (void) FormatLocaleFile(stderr, "# -----\n" );
1061 (void) FormatLocaleFile(stderr, "dux=%lf; dvx=%lf; duy=%lf; dvy=%lf;\n",
1062 dux, dvx, duy, dvy);
1063#endif
1064
1065 /* Find Ellipse Coefficients such that
1066 A*u^2 + B*u*v + C*v^2 = F
1067 With u,v relative to point around which we are resampling.
1068 And the given scaling dx,dy vectors in u,v space
1069 du/dx,dv/dx and du/dy,dv/dy
1070 */
1071#if EWA
1072 /* Direct conversion of derivatives into elliptical coefficients
1073 However when magnifying images, the scaling vectors will be small
1074 resulting in a ellipse that is too small to sample properly.
1075 As such we need to clamp the major/minor axis to a minimum of 1.0
1076 to prevent it getting too small.
1077 */
1078#if EWA_CLAMP
1079 { double major_mag,
1080 minor_mag,
1081 major_x,
1082 major_y,
1083 minor_x,
1084 minor_y;
1085
1086 ClampUpAxes(dux,dvx,duy,dvy, &major_mag, &minor_mag,
1087 &major_x, &major_y, &minor_x, &minor_y);
1088 major_x *= major_mag; major_y *= major_mag;
1089 minor_x *= minor_mag; minor_y *= minor_mag;
1090#if DEBUG_ELLIPSE
1091 (void) FormatLocaleFile(stderr, "major_x=%lf; major_y=%lf; minor_x=%lf; minor_y=%lf;\n",
1092 major_x, major_y, minor_x, minor_y);
1093#endif
1094 A = major_y*major_y+minor_y*minor_y;
1095 B = -2.0*(major_x*major_y+minor_x*minor_y);
1096 C = major_x*major_x+minor_x*minor_x;
1097 F = major_mag*minor_mag;
1098 F *= F; /* square it */
1099 }
1100#else /* raw unclamped EWA */
1101 A = dvx*dvx+dvy*dvy;
1102 B = -2.0*(dux*dvx+duy*dvy);
1103 C = dux*dux+duy*duy;
1104 F = dux*dvy-duy*dvx;
1105 F *= F; /* square it */
1106#endif /* EWA_CLAMP */
1107
1108#else /* HQ_EWA */
1109 /*
1110 This Paul Heckbert's "Higher Quality EWA" formula, from page 60 in his
1111 thesis, which adds a unit circle to the elliptical area so as to do both
1112 Reconstruction and Prefiltering of the pixels in the resampling. It also
1113 means it is always likely to have at least 4 pixels within the area of the
1114 ellipse, for weighted averaging. No scaling will result with F == 4.0 and
1115 a circle of radius 2.0, and F smaller than this means magnification is
1116 being used.
1117
1118 NOTE: This method produces a very blurry result at near unity scale while
1119 producing perfect results for strong minification and magnifications.
1120
1121 However filter support is fixed to 2.0 (no good for Windowed Sinc filters)
1122 */
1123 A = dvx*dvx+dvy*dvy+1;
1124 B = -2.0*(dux*dvx+duy*dvy);
1125 C = dux*dux+duy*duy+1;
1126 F = A*C - B*B/4;
1127#endif
1128
1129#if DEBUG_ELLIPSE
1130 (void) FormatLocaleFile(stderr, "A=%lf; B=%lf; C=%lf; F=%lf\n", A,B,C,F);
1131
1132 /* Figure out the various information directly about the ellipse.
1133 This information currently not needed at this time, but may be
1134 needed later for better limit determination.
1135
1136 It is also good to have as a record for future debugging
1137 */
1138 { double alpha, beta, gamma, Major, Minor;
1139 double Eccentricity, Ellipse_Area, Ellipse_Angle;
1140
1141 alpha = A+C;
1142 beta = A-C;
1143 gamma = sqrt(beta*beta + B*B );
1144
1145 if ( alpha - gamma <= MagickEpsilon )
1146 Major=MagickMaximumValue;
1147 else
1148 Major=sqrt(2*F/(alpha - gamma));
1149 Minor = sqrt(2*F/(alpha + gamma));
1150
1151 (void) FormatLocaleFile(stderr, "# Major=%lf; Minor=%lf\n", Major, Minor );
1152
1153 /* other information about ellipse include... */
1154 Eccentricity = Major/Minor;
1155 Ellipse_Area = MagickPI*Major*Minor;
1156 Ellipse_Angle = atan2(B, A-C);
1157
1158 (void) FormatLocaleFile(stderr, "# Angle=%lf Area=%lf\n",
1159 (double) RadiansToDegrees(Ellipse_Angle), Ellipse_Area);
1160 }
1161#endif
1162
1163 /* If one or both of the scaling vectors is impossibly large
1164 (producing a very large raw F value), we may as well not bother
1165 doing any form of resampling since resampled area is very large.
1166 In this case some alternative means of pixel sampling, such as
1167 the average of the whole image is needed to get a reasonable
1168 result. Calculate only as needed.
1169 */
1170 if ( (4*A*C - B*B) > MagickMaximumValue ) {
1171 resample_filter->limit_reached = MagickTrue;
1172 return;
1173 }
1174
1175 /* Scale ellipse to match the filters support
1176 (that is, multiply F by the square of the support)
1177 Simpler to just multiply it by the support twice!
1178 */
1179 F *= resample_filter->support;
1180 F *= resample_filter->support;
1181
1182 /* Orthogonal bounds of the ellipse */
1183 resample_filter->Ulimit = sqrt(C*F/(A*C-0.25*B*B));
1184 resample_filter->Vlimit = sqrt(A*F/(A*C-0.25*B*B));
1185
1186 /* Horizontally aligned parallelogram fitted to Ellipse */
1187 resample_filter->Uwidth = sqrt(F/A); /* Half of the parallelogram width */
1188 resample_filter->slope = -B/(2.0*A); /* Reciprocal slope of the parallelogram */
1189
1190#if DEBUG_ELLIPSE
1191 (void) FormatLocaleFile(stderr, "Ulimit=%lf; Vlimit=%lf; UWidth=%lf; Slope=%lf;\n",
1192 resample_filter->Ulimit, resample_filter->Vlimit,
1193 resample_filter->Uwidth, resample_filter->slope );
1194#endif
1195
1196 /* Check the absolute area of the parallelogram involved.
1197 * This limit needs more work, as it is too slow for larger images
1198 * with tiled views of the horizon.
1199 */
1200 if ( (resample_filter->Uwidth * resample_filter->Vlimit)
1201 > (4.0*resample_filter->image_area)) {
1202 resample_filter->limit_reached = MagickTrue;
1203 return;
1204 }
1205
1206 /* Scale ellipse formula to directly index the Filter Lookup Table */
1207 { double scale;
1208#if FILTER_LUT
1209 /* scale so that F = WLUT_WIDTH; -- hardcoded */
1210 scale=(double) WLUT_WIDTH*PerceptibleReciprocal(F);
1211#else
1212 /* scale so that F = resample_filter->F (support^2) */
1213 scale=resample_filter->F*PerceptibleReciprocal(F);
1214#endif
1215 resample_filter->A = A*scale;
1216 resample_filter->B = B*scale;
1217 resample_filter->C = C*scale;
1218 }
1219}
1220
1221/*
1222%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1223% %
1224% %
1225% %
1226% S e t R e s a m p l e F i l t e r %
1227% %
1228% %
1229% %
1230%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1231%
1232% SetResampleFilter() set the resampling filter lookup table based on a
1233% specific filter. Note that the filter is used as a radial filter not as a
1234% two pass orthogonally aligned resampling filter.
1235%
1236% The format of the SetResampleFilter method is:
1237%
1238% void SetResampleFilter(ResampleFilter *resample_filter,
1239% const FilterType filter)
1240%
1241% A description of each parameter follows:
1242%
1243% o resample_filter: resampling information structure
1244%
1245% o filter: the resize filter for elliptical weighting LUT
1246%
1247*/
1248MagickExport void SetResampleFilter(ResampleFilter *resample_filter,
1249 const FilterType filter)
1250{
1252 *resize_filter;
1253
1254 assert(resample_filter != (ResampleFilter *) NULL);
1255 assert(resample_filter->signature == MagickCoreSignature);
1256
1257 resample_filter->do_interpolate = MagickFalse;
1258 resample_filter->filter = filter;
1259
1260 /* Default cylindrical filter is a Cubic Keys filter */
1261 if ( filter == UndefinedFilter )
1262 resample_filter->filter = RobidouxFilter;
1263
1264 if ( resample_filter->filter == PointFilter ) {
1265 resample_filter->do_interpolate = MagickTrue;
1266 return; /* EWA turned off - nothing more to do */
1267 }
1268
1269 resize_filter = AcquireResizeFilter(resample_filter->image,
1270 resample_filter->filter,MagickTrue,resample_filter->exception);
1271 if (resize_filter == (ResizeFilter *) NULL) {
1272 (void) ThrowMagickException(resample_filter->exception,GetMagickModule(),
1273 ModuleError, "UnableToSetFilteringValue",
1274 "Fall back to Interpolated 'Point' filter");
1275 resample_filter->filter = PointFilter;
1276 resample_filter->do_interpolate = MagickTrue;
1277 return; /* EWA turned off - nothing more to do */
1278 }
1279
1280 /* Get the practical working support for the filter,
1281 * after any API call blur factors have been accounted for.
1282 */
1283#if EWA
1284 resample_filter->support = GetResizeFilterSupport(resize_filter);
1285#else
1286 resample_filter->support = 2.0; /* fixed support size for HQ-EWA */
1287#endif
1288
1289#if FILTER_LUT
1290 /* Fill the LUT with the weights from the selected filter function */
1291 { int
1292 Q;
1293 double
1294 r_scale;
1295
1296 /* Scale radius so the filter LUT covers the full support range */
1297 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1298 for(Q=0; Q<WLUT_WIDTH; Q++)
1299 resample_filter->filter_lut[Q] = (double)
1300 GetResizeFilterWeight(resize_filter,sqrt((double)Q)*r_scale);
1301
1302 /* finished with the resize filter */
1303 resize_filter = DestroyResizeFilter(resize_filter);
1304 }
1305#else
1306 /* save the filter and the scaled ellipse bounds needed for filter */
1307 resample_filter->filter_def = resize_filter;
1308 resample_filter->F = resample_filter->support*resample_filter->support;
1309#endif
1310
1311 /*
1312 Adjust the scaling of the default unit circle
1313 This assumes that any real scaling changes will always
1314 take place AFTER the filter method has been initialized.
1315 */
1316 ScaleResampleFilter(resample_filter, 1.0, 0.0, 0.0, 1.0);
1317
1318#if 0
1319 /*
1320 This is old code kept as a reference only. Basically it generates
1321 a Gaussian bell curve, with sigma = 0.5 if the support is 2.0
1322
1323 Create Normal Gaussian 2D Filter Weighted Lookup Table.
1324 A normal EWA guassual lookup would use exp(Q*ALPHA)
1325 where Q = distance squared from 0.0 (center) to 1.0 (edge)
1326 and ALPHA = -4.0*ln(2.0) ==> -2.77258872223978123767
1327 The table is of length 1024, and equates to support radius of 2.0
1328 thus needs to be scaled by ALPHA*4/1024 and any blur factor squared
1329
1330 The it comes from reference code provided by Fred Weinhaus.
1331 */
1332 r_scale = -2.77258872223978123767/(WLUT_WIDTH*blur*blur);
1333 for(Q=0; Q<WLUT_WIDTH; Q++)
1334 resample_filter->filter_lut[Q] = exp((double)Q*r_scale);
1335 resample_filter->support = WLUT_WIDTH;
1336#endif
1337
1338#if FILTER_LUT
1339#if defined(MAGICKCORE_OPENMP_SUPPORT)
1340 #pragma omp single
1341#endif
1342 {
1343 if (IsStringTrue(GetImageArtifact(resample_filter->image,
1344 "resample:verbose")) != MagickFalse)
1345 {
1346 int
1347 Q;
1348 double
1349 r_scale;
1350
1351 /* Debug output of the filter weighting LUT
1352 Gnuplot the LUT data, the x scale index has been adjusted
1353 plot [0:2][-.2:1] "lut.dat" with lines
1354 The filter values should be normalized for comparison
1355 */
1356 printf("#\n");
1357 printf("# Resampling Filter LUT (%d values) for '%s' filter\n",
1358 WLUT_WIDTH, CommandOptionToMnemonic(MagickFilterOptions,
1359 resample_filter->filter) );
1360 printf("#\n");
1361 printf("# Note: values in table are using a squared radius lookup.\n");
1362 printf("# As such its distribution is not uniform.\n");
1363 printf("#\n");
1364 printf("# The X value is the support distance for the Y weight\n");
1365 printf("# so you can use gnuplot to plot this cylindrical filter\n");
1366 printf("# plot [0:2][-.2:1] \"lut.dat\" with lines\n");
1367 printf("#\n");
1368
1369 /* Scale radius so the filter LUT covers the full support range */
1370 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1371 for(Q=0; Q<WLUT_WIDTH; Q++)
1372 printf("%8.*g %.*g\n",
1373 GetMagickPrecision(),sqrt((double)Q)*r_scale,
1374 GetMagickPrecision(),resample_filter->filter_lut[Q] );
1375 printf("\n\n"); /* generate a 'break' in gnuplot if multiple outputs */
1376 }
1377 /* Output the above once only for each image, and each setting
1378 (void) DeleteImageArtifact(resample_filter->image,"resample:verbose");
1379 */
1380 }
1381#endif /* FILTER_LUT */
1382 return;
1383}
1384
1385/*
1386%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1387% %
1388% %
1389% %
1390% S e t R e s a m p l e F i l t e r I n t e r p o l a t e M e t h o d %
1391% %
1392% %
1393% %
1394%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1395%
1396% SetResampleFilterInterpolateMethod() sets the resample filter interpolation
1397% method.
1398%
1399% The format of the SetResampleFilterInterpolateMethod method is:
1400%
1401% MagickBooleanType SetResampleFilterInterpolateMethod(
1402% ResampleFilter *resample_filter,const InterpolateMethod method)
1403%
1404% A description of each parameter follows:
1405%
1406% o resample_filter: the resample filter.
1407%
1408% o method: the interpolation method.
1409%
1410*/
1411MagickExport MagickBooleanType SetResampleFilterInterpolateMethod(
1412 ResampleFilter *resample_filter,const PixelInterpolateMethod method)
1413{
1414 assert(resample_filter != (ResampleFilter *) NULL);
1415 assert(resample_filter->signature == MagickCoreSignature);
1416 assert(resample_filter->image != (Image *) NULL);
1417 if (IsEventLogging() != MagickFalse)
1418 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1419 resample_filter->image->filename);
1420 resample_filter->interpolate=method;
1421 return(MagickTrue);
1422}
1423
1424/*
1425%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1426% %
1427% %
1428% %
1429% S e t R e s a m p l e F i l t e r V i r t u a l P i x e l M e t h o d %
1430% %
1431% %
1432% %
1433%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1434%
1435% SetResampleFilterVirtualPixelMethod() changes the virtual pixel method
1436% associated with the specified resample filter.
1437%
1438% The format of the SetResampleFilterVirtualPixelMethod method is:
1439%
1440% MagickBooleanType SetResampleFilterVirtualPixelMethod(
1441% ResampleFilter *resample_filter,const VirtualPixelMethod method)
1442%
1443% A description of each parameter follows:
1444%
1445% o resample_filter: the resample filter.
1446%
1447% o method: the virtual pixel method.
1448%
1449*/
1450MagickExport MagickBooleanType SetResampleFilterVirtualPixelMethod(
1451 ResampleFilter *resample_filter,const VirtualPixelMethod method)
1452{
1453 assert(resample_filter != (ResampleFilter *) NULL);
1454 assert(resample_filter->signature == MagickCoreSignature);
1455 assert(resample_filter->image != (Image *) NULL);
1456 if (IsEventLogging() != MagickFalse)
1457 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1458 resample_filter->image->filename);
1459 resample_filter->virtual_pixel=method;
1460 if (method != UndefinedVirtualPixelMethod)
1461 (void) SetCacheViewVirtualPixelMethod(resample_filter->view,method);
1462 return(MagickTrue);
1463}