2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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 %
13 % MagickCore Pixel Resampling Methods %
21 % Copyright 1999-2012 ImageMagick Studio LLC, a non-profit organization %
22 % dedicated to making software imaging solutions freely available. %
24 % You may not use this file except in compliance with the License. You may %
25 % obtain a copy of the License at %
27 % http://www.imagemagick.org/script/license.php %
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. %
35 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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/pixel.h"
56 #include "MagickCore/pixel-accessor.h"
57 #include "MagickCore/quantum.h"
58 #include "MagickCore/random_.h"
59 #include "MagickCore/resample.h"
60 #include "MagickCore/resize.h"
61 #include "MagickCore/resize-private.h"
62 #include "MagickCore/token.h"
63 #include "MagickCore/transform.h"
64 #include "MagickCore/signature-private.h"
65 #include "MagickCore/utility.h"
66 #include "MagickCore/utility-private.h"
67 #include "MagickCore/option.h"
69 EWA Resampling Options
72 /* select ONE resampling method */
73 #define EWA 1 /* Normal EWA handling - raw or clamped */
74 /* if 0 then use "High Quality EWA" */
75 #define EWA_CLAMP 1 /* EWA Clamping from Nicolas Robidoux */
77 #define FILTER_LUT 1 /* Use a LUT rather then direct filter calls */
79 /* output debugging information */
80 #define DEBUG_ELLIPSE 0 /* output ellipse info for debug */
81 #define DEBUG_HIT_MISS 0 /* output hit/miss pixels (as gnuplot commands) */
82 #define DEBUG_NO_PIXEL_HIT 0 /* Make pixels that fail to hit anything - RED */
85 #define WLUT_WIDTH 1024 /* size of the filter cache */
91 struct _ResampleFilter
105 /* Information about image being resampled */
109 PixelInterpolateMethod
118 /* processing settings needed */
127 /* current ellipitical area being resampled around center point */
130 Vlimit, Ulimit, Uwidth, slope;
133 /* LUT of weights for filtered average in elliptical area */
135 filter_lut[WLUT_WIDTH];
137 /* Use a Direct call to the filter functions */
145 /* the practical working support of the filter */
154 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
158 % A c q u i r e R e s a m p l e I n f o %
162 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
164 % AcquireResampleFilter() initializes the information resample needs do to a
165 % scaled lookup of a color from an image, using area sampling.
167 % The algorithm is based on a Elliptical Weighted Average, where the pixels
168 % found in a large elliptical area is averaged together according to a
169 % weighting (filter) function. For more details see "Fundamentals of Texture
170 % Mapping and Image Warping" a master's thesis by Paul.S.Heckbert, June 17,
171 % 1989. Available for free from, http://www.cs.cmu.edu/~ph/
173 % As EWA resampling (or any sort of resampling) can require a lot of
174 % calculations to produce a distorted scaling of the source image for each
175 % output pixel, the ResampleFilter structure generated holds that information
176 % between individual image resampling.
178 % This function will make the appropriate AcquireCacheView() calls
179 % to view the image, calling functions do not need to open a cache view.
182 % resample_filter=AcquireResampleFilter(image,exception);
183 % SetResampleFilter(resample_filter, GaussianFilter);
184 % for (y=0; y < (ssize_t) image->rows; y++) {
185 % for (x=0; x < (ssize_t) image->columns; x++) {
187 % ScaleResampleFilter(resample_filter, ... scaling vectors ...);
188 % (void) ResamplePixelColor(resample_filter,u,v,&pixel);
189 % ... assign resampled pixel value ...
192 % DestroyResampleFilter(resample_filter);
194 % The format of the AcquireResampleFilter method is:
196 % ResampleFilter *AcquireResampleFilter(const Image *image,
197 % ExceptionInfo *exception)
199 % A description of each parameter follows:
201 % o image: the image.
203 % o exception: return any errors or warnings in this structure.
206 MagickExport ResampleFilter *AcquireResampleFilter(const Image *image,
207 ExceptionInfo *exception)
209 register ResampleFilter
212 assert(image != (Image *) NULL);
213 assert(image->signature == MagickSignature);
214 if (image->debug != MagickFalse)
215 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
216 assert(exception != (ExceptionInfo *) NULL);
217 assert(exception->signature == MagickSignature);
219 resample_filter=(ResampleFilter *) AcquireMagickMemory(
220 sizeof(*resample_filter));
221 if (resample_filter == (ResampleFilter *) NULL)
222 ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
223 (void) ResetMagickMemory(resample_filter,0,sizeof(*resample_filter));
225 resample_filter->exception=exception;
226 resample_filter->image=ReferenceImage((Image *) image);
227 resample_filter->view=AcquireVirtualCacheView(resample_filter->image,exception);
229 resample_filter->debug=IsEventLogging();
230 resample_filter->signature=MagickSignature;
232 resample_filter->image_area=(ssize_t) (image->columns*image->rows);
233 resample_filter->average_defined = MagickFalse;
235 /* initialise the resampling filter settings */
236 SetResampleFilter(resample_filter, image->filter);
237 (void) SetResampleFilterInterpolateMethod(resample_filter,image->interpolate);
238 (void) SetResampleFilterVirtualPixelMethod(resample_filter,
239 GetImageVirtualPixelMethod(image));
240 return(resample_filter);
244 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
248 % D e s t r o y R e s a m p l e I n f o %
252 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
254 % DestroyResampleFilter() finalizes and cleans up the resampling
255 % resample_filter as returned by AcquireResampleFilter(), freeing any memory
256 % or other information as needed.
258 % The format of the DestroyResampleFilter method is:
260 % ResampleFilter *DestroyResampleFilter(ResampleFilter *resample_filter)
262 % A description of each parameter follows:
264 % o resample_filter: resampling information structure
267 MagickExport ResampleFilter *DestroyResampleFilter(
268 ResampleFilter *resample_filter)
270 assert(resample_filter != (ResampleFilter *) NULL);
271 assert(resample_filter->signature == MagickSignature);
272 assert(resample_filter->image != (Image *) NULL);
273 if (resample_filter->debug != MagickFalse)
274 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
275 resample_filter->image->filename);
276 resample_filter->view=DestroyCacheView(resample_filter->view);
277 resample_filter->image=DestroyImage(resample_filter->image);
279 resample_filter->filter_def=DestroyResizeFilter(resample_filter->filter_def);
281 resample_filter->signature=(~MagickSignature);
282 resample_filter=(ResampleFilter *) RelinquishMagickMemory(resample_filter);
283 return(resample_filter);
287 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
291 % R e s a m p l e P i x e l C o l o r %
295 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
297 % ResamplePixelColor() samples the pixel values surrounding the location
298 % given using an elliptical weighted average, at the scale previously
299 % calculated, and in the most efficent manner possible for the
300 % VirtualPixelMethod setting.
302 % The format of the ResamplePixelColor method is:
304 % MagickBooleanType ResamplePixelColor(ResampleFilter *resample_filter,
305 % const double u0,const double v0,PixelInfo *pixel,
306 % ExceptionInfo *exception)
308 % A description of each parameter follows:
310 % o resample_filter: the resample filter.
312 % o u0,v0: A double representing the center of the area to resample,
313 % The distortion transformed transformed x,y coordinate.
315 % o pixel: the resampled pixel is returned here.
317 % o exception: return any errors or warnings in this structure.
320 MagickExport MagickBooleanType ResamplePixelColor(
321 ResampleFilter *resample_filter,const double u0,const double v0,
322 PixelInfo *pixel,ExceptionInfo *exception)
327 ssize_t u,v, v1, v2, uw, hit;
330 double divisor_c,divisor_m;
331 register double weight;
332 register const Quantum *pixels;
333 assert(resample_filter != (ResampleFilter *) NULL);
334 assert(resample_filter->signature == MagickSignature);
337 /* GetPixelInfo(resample_filter->image,pixel); */
338 if ( resample_filter->do_interpolate ) {
339 status=InterpolatePixelInfo(resample_filter->image,resample_filter->view,
340 resample_filter->interpolate,u0,v0,pixel,resample_filter->exception);
345 (void) FormatLocaleFile(stderr, "u0=%lf; v0=%lf;\n", u0, v0);
349 Does resample area Miss the image?
350 And is that area a simple solid color - then return that color
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
363 || v0 + resample_filter->Vlimit < 0.0
364 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows
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 )
374 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
375 && v0 + resample_filter->Vlimit < 0.0 )
376 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
377 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows )
381 case HorizontalTileVirtualPixelMethod:
382 if ( v0 + resample_filter->Vlimit < 0.0
383 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows
385 hit++; /* outside the horizontally tiled images. */
387 case VerticalTileVirtualPixelMethod:
388 if ( u0 + resample_filter->Ulimit < 0.0
389 || u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
391 hit++; /* outside the vertically tiled images. */
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+32.0 )
397 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+32.0
398 && v0 + resample_filter->Vlimit < -32.0 )
399 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+32.0
400 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows+32.0 )
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 */
414 /* whole area is a solid color -- just return that color */
415 status=InterpolatePixelInfo(resample_filter->image,
416 resample_filter->view,IntegerInterpolatePixel,u0,v0,pixel,
417 resample_filter->exception);
422 Scaling limits reached, return an 'averaged' result.
424 if ( resample_filter->limit_reached ) {
425 switch ( resample_filter->virtual_pixel ) {
426 /* This is always handled by the above, so no need.
427 case BackgroundVirtualPixelMethod:
428 case ConstantVirtualPixelMethod:
429 case TransparentVirtualPixelMethod:
430 case GrayVirtualPixelMethod,
431 case WhiteVirtualPixelMethod
432 case MaskVirtualPixelMethod:
434 case UndefinedVirtualPixelMethod:
435 case EdgeVirtualPixelMethod:
436 case DitherVirtualPixelMethod:
437 case HorizontalTileEdgeVirtualPixelMethod:
438 case VerticalTileEdgeVirtualPixelMethod:
439 /* We need an average edge pixel, from the correct edge!
440 How should I calculate an average edge color?
441 Just returning an averaged neighbourhood,
442 works well in general, but falls down for TileEdge methods.
443 This needs to be done properly!!!!!!
445 status=InterpolatePixelInfo(resample_filter->image,
446 resample_filter->view,AverageInterpolatePixel,u0,v0,pixel,
447 resample_filter->exception);
449 case HorizontalTileVirtualPixelMethod:
450 case VerticalTileVirtualPixelMethod:
451 /* just return the background pixel - Is there more direct way? */
452 status=InterpolatePixelInfo(resample_filter->image,
453 resample_filter->view,IntegerInterpolatePixel,-1.0,-1.0,pixel,
454 resample_filter->exception);
456 case TileVirtualPixelMethod:
457 case MirrorVirtualPixelMethod:
458 case RandomVirtualPixelMethod:
459 case CheckerTileVirtualPixelMethod:
461 /* generate a average color of the WHOLE image */
462 if ( resample_filter->average_defined == MagickFalse ) {
469 GetPixelInfo(resample_filter->image,(PixelInfo *)
470 &resample_filter->average_pixel);
471 resample_filter->average_defined=MagickTrue;
473 /* Try to get an averaged pixel color of whole image */
474 average_image=ResizeImage(resample_filter->image,1,1,BoxFilter,
475 resample_filter->exception);
476 if (average_image == (Image *) NULL)
478 *pixel=resample_filter->average_pixel; /* FAILED */
481 average_view=AcquireVirtualCacheView(average_image,exception);
482 pixels=GetCacheViewVirtualPixels(average_view,0,0,1,1,
483 resample_filter->exception);
484 if (pixels == (const Quantum *) NULL) {
485 average_view=DestroyCacheView(average_view);
486 average_image=DestroyImage(average_image);
487 *pixel=resample_filter->average_pixel; /* FAILED */
490 GetPixelInfoPixel(resample_filter->image,pixels,
491 &(resample_filter->average_pixel));
492 average_view=DestroyCacheView(average_view);
493 average_image=DestroyImage(average_image);
495 if ( resample_filter->virtual_pixel == CheckerTileVirtualPixelMethod )
497 /* CheckerTile is a alpha blend of the image's average pixel
498 color and the current background color */
500 /* image's average pixel color */
501 weight = QuantumScale*((MagickRealType)
502 resample_filter->average_pixel.alpha);
503 resample_filter->average_pixel.red *= weight;
504 resample_filter->average_pixel.green *= weight;
505 resample_filter->average_pixel.blue *= weight;
508 /* background color */
509 weight = QuantumScale*((MagickRealType)
510 resample_filter->image->background_color.alpha);
511 resample_filter->average_pixel.red +=
512 weight*resample_filter->image->background_color.red;
513 resample_filter->average_pixel.green +=
514 weight*resample_filter->image->background_color.green;
515 resample_filter->average_pixel.blue +=
516 weight*resample_filter->image->background_color.blue;
517 resample_filter->average_pixel.alpha +=
518 resample_filter->image->background_color.alpha;
522 resample_filter->average_pixel.red /= divisor_c;
523 resample_filter->average_pixel.green /= divisor_c;
524 resample_filter->average_pixel.blue /= divisor_c;
525 resample_filter->average_pixel.alpha /= 2; /* 50% blend */
529 *pixel=resample_filter->average_pixel;
536 Initialize weighted average data collection
541 pixel->red = pixel->green = pixel->blue = 0.0;
542 if (pixel->colorspace == CMYKColorspace)
544 if (pixel->matte != MagickFalse)
548 Determine the parellelogram bounding box fitted to the ellipse
549 centered at u0,v0. This area is bounding by the lines...
551 v1 = (ssize_t)ceil(v0 - resample_filter->Vlimit); /* range of scan lines */
552 v2 = (ssize_t)floor(v0 + resample_filter->Vlimit);
554 /* scan line start and width accross the parallelogram */
555 u1 = u0 + (v1-v0)*resample_filter->slope - resample_filter->Uwidth;
556 uw = (ssize_t)(2.0*resample_filter->Uwidth)+1;
559 (void) FormatLocaleFile(stderr, "v1=%ld; v2=%ld\n", (long)v1, (long)v2);
560 (void) FormatLocaleFile(stderr, "u1=%ld; uw=%ld\n", (long)u1, (long)uw);
562 # define DEBUG_HIT_MISS 0 /* only valid if DEBUG_ELLIPSE is enabled */
566 Do weighted resampling of all pixels, within the scaled ellipse,
567 bound by a Parellelogram fitted to the ellipse.
569 DDQ = 2*resample_filter->A;
570 for( v=v1; v<=v2; v++ ) {
572 long uu = ceil(u1); /* actual pixel location (for debug only) */
573 (void) FormatLocaleFile(stderr, "# scan line from pixel %ld, %ld\n", (long)uu, (long)v);
575 u = (ssize_t)ceil(u1); /* first pixel in scanline */
576 u1 += resample_filter->slope; /* start of next scan line */
579 /* location of this first pixel, relative to u0,v0 */
583 /* Q = ellipse quotent ( if Q<F then pixel is inside ellipse) */
584 Q = (resample_filter->A*U + resample_filter->B*V)*U + resample_filter->C*V*V;
585 DQ = resample_filter->A*(2.0*U+1) + resample_filter->B*V;
587 /* get the scanline of pixels for this v */
588 pixels=GetCacheViewVirtualPixels(resample_filter->view,u,v,(size_t) uw,
589 1,resample_filter->exception);
590 if (pixels == (const Quantum *) NULL)
593 /* count up the weighted pixel colors */
594 for( u=0; u<uw; u++ ) {
596 /* Note that the ellipse has been pre-scaled so F = WLUT_WIDTH */
597 if ( Q < (double)WLUT_WIDTH ) {
598 weight = resample_filter->filter_lut[(int)Q];
600 /* Note that the ellipse has been pre-scaled so F = support^2 */
601 if ( Q < (double)resample_filter->F ) {
602 weight = GetResizeFilterWeight(resample_filter->filter_def,
603 sqrt(Q)); /* a SquareRoot! Arrggghhhhh... */
606 pixel->alpha += weight*GetPixelAlpha(resample_filter->image,pixels);
609 if (pixel->matte != MagickFalse)
610 weight *= QuantumScale*((MagickRealType) GetPixelAlpha(resample_filter->image,pixels));
611 pixel->red += weight*GetPixelRed(resample_filter->image,pixels);
612 pixel->green += weight*GetPixelGreen(resample_filter->image,pixels);
613 pixel->blue += weight*GetPixelBlue(resample_filter->image,pixels);
614 if (pixel->colorspace == CMYKColorspace)
615 pixel->black += weight*GetPixelBlack(resample_filter->image,pixels);
620 /* mark the pixel according to hit/miss of the ellipse */
621 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
622 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
623 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
624 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
626 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
627 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
628 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
629 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
635 pixels+=GetPixelChannels(resample_filter->image);
641 (void) FormatLocaleFile(stderr, "Hit=%ld; Total=%ld;\n", (long)hit, (long)uw*(v2-v1) );
645 Result sanity check -- this should NOT happen
648 /* not enough pixels in resampling, resort to direct interpolation */
649 #if DEBUG_NO_PIXEL_HIT
650 pixel->alpha = pixel->red = pixel->green = pixel->blue = 0;
651 pixel->red = QuantumRange; /* show pixels for which EWA fails */
653 status=InterpolatePixelInfo(resample_filter->image,
654 resample_filter->view,resample_filter->interpolate,u0,v0,pixel,
655 resample_filter->exception);
661 Finialize results of resampling
663 divisor_m = 1.0/divisor_m;
664 pixel->alpha = (MagickRealType) ClampToQuantum(divisor_m*pixel->alpha);
665 divisor_c = 1.0/divisor_c;
666 pixel->red = (MagickRealType) ClampToQuantum(divisor_c*pixel->red);
667 pixel->green = (MagickRealType) ClampToQuantum(divisor_c*pixel->green);
668 pixel->blue = (MagickRealType) ClampToQuantum(divisor_c*pixel->blue);
669 if (pixel->colorspace == CMYKColorspace)
670 pixel->black = (MagickRealType) ClampToQuantum(divisor_c*pixel->black);
676 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
680 - C l a m p U p A x e s %
684 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
686 % ClampUpAxes() function converts the input vectors into a major and
687 % minor axis unit vectors, and their magnitude. This allows us to
688 % ensure that the ellipse generated is never smaller than the unit
689 % circle and thus never too small for use in EWA resampling.
691 % This purely mathematical 'magic' was provided by Professor Nicolas
692 % Robidoux and his Masters student Chantal Racette.
694 % Reference: "We Recommend Singular Value Decomposition", David Austin
695 % http://www.ams.org/samplings/feature-column/fcarc-svd
697 % By generating major and minor axis vectors, we can actually use the
698 % ellipse in its "canonical form", by remapping the dx,dy of the
699 % sampled point into distances along the major and minor axis unit
702 % Reference: http://en.wikipedia.org/wiki/Ellipse#Canonical_form
704 static inline void ClampUpAxes(const double dux,
710 double *major_unit_x,
711 double *major_unit_y,
712 double *minor_unit_x,
713 double *minor_unit_y)
716 * ClampUpAxes takes an input 2x2 matrix
718 * [ a b ] = [ dux duy ]
719 * [ c d ] = [ dvx dvy ]
721 * and computes from it the major and minor axis vectors [major_x,
722 * major_y] and [minor_x,minor_y] of the smallest ellipse containing
723 * both the unit disk and the ellipse which is the image of the unit
724 * disk by the linear transformation
726 * [ dux duy ] [S] = [s]
727 * [ dvx dvy ] [T] = [t]
729 * (The vector [S,T] is the difference between a position in output
730 * space and [X,Y]; the vector [s,t] is the difference between a
731 * position in input space and [x,y].)
736 * major_mag is the half-length of the major axis of the "new"
739 * minor_mag is the half-length of the minor axis of the "new"
742 * major_unit_x is the x-coordinate of the major axis direction vector
743 * of both the "old" and "new" ellipses.
745 * major_unit_y is the y-coordinate of the major axis direction vector.
747 * minor_unit_x is the x-coordinate of the minor axis direction vector.
749 * minor_unit_y is the y-coordinate of the minor axis direction vector.
751 * Unit vectors are useful for computing projections, in particular,
752 * to compute the distance between a point in output space and the
753 * center of a unit disk in output space, using the position of the
754 * corresponding point [s,t] in input space. Following the clamping,
755 * the square of this distance is
757 * ( ( s * major_unit_x + t * major_unit_y ) / major_mag )^2
759 * ( ( s * minor_unit_x + t * minor_unit_y ) / minor_mag )^2
761 * If such distances will be computed for many [s,t]'s, it makes
762 * sense to actually compute the reciprocal of major_mag and
763 * minor_mag and multiply them by the above unit lengths.
765 * Now, if you want to modify the input pair of tangent vectors so
766 * that it defines the modified ellipse, all you have to do is set
768 * newdux = major_mag * major_unit_x
769 * newdvx = major_mag * major_unit_y
770 * newduy = minor_mag * minor_unit_x = minor_mag * -major_unit_y
771 * newdvy = minor_mag * minor_unit_y = minor_mag * major_unit_x
773 * and use these tangent vectors as if they were the original ones.
774 * Usually, this is a drastic change in the tangent vectors even if
775 * the singular values are not clamped; for example, the minor axis
776 * vector always points in a direction which is 90 degrees
777 * counterclockwise from the direction of the major axis vector.
782 * GOAL: Fix things so that the pullback, in input space, of a disk
783 * of radius r in output space is an ellipse which contains, at
784 * least, a disc of radius r. (Make this hold for any r>0.)
786 * ESSENCE OF THE METHOD: Compute the product of the first two
787 * factors of an SVD of the linear transformation defining the
788 * ellipse and make sure that both its columns have norm at least 1.
789 * Because rotations and reflexions map disks to themselves, it is
790 * not necessary to compute the third (rightmost) factor of the SVD.
792 * DETAILS: Find the singular values and (unit) left singular
793 * vectors of Jinv, clampling up the singular values to 1, and
794 * multiply the unit left singular vectors by the new singular
795 * values in order to get the minor and major ellipse axis vectors.
797 * Image resampling context:
799 * The Jacobian matrix of the transformation at the output point
800 * under consideration is defined as follows:
802 * Consider the transformation (x,y) -> (X,Y) from input locations
803 * to output locations. (Anthony Thyssen, elsewhere in resample.c,
804 * uses the notation (u,v) -> (x,y).)
806 * The Jacobian matrix of the transformation at (x,y) is equal to
808 * J = [ A, B ] = [ dX/dx, dX/dy ]
809 * [ C, D ] [ dY/dx, dY/dy ]
811 * that is, the vector [A,C] is the tangent vector corresponding to
812 * input changes in the horizontal direction, and the vector [B,D]
813 * is the tangent vector corresponding to input changes in the
814 * vertical direction.
816 * In the context of resampling, it is natural to use the inverse
817 * Jacobian matrix Jinv because resampling is generally performed by
818 * pulling pixel locations in the output image back to locations in
819 * the input image. Jinv is
821 * Jinv = [ a, b ] = [ dx/dX, dx/dY ]
822 * [ c, d ] [ dy/dX, dy/dY ]
824 * Note: Jinv can be computed from J with the following matrix
827 * Jinv = 1/(A*D-B*C) [ D, -B ]
830 * What we do is modify Jinv so that it generates an ellipse which
831 * is as close as possible to the original but which contains the
832 * unit disk. This can be accomplished as follows:
838 * be an SVD decomposition of Jinv. (The SVD is not unique, but the
839 * final ellipse does not depend on the particular SVD.)
841 * We could clamp up the entries of the diagonal matrix Sigma so
842 * that they are at least 1, and then set
844 * Jinv = U newSigma V^T.
846 * However, we do not need to compute V for the following reason:
847 * V^T is an orthogonal matrix (that is, it represents a combination
848 * of rotations and reflexions) so that it maps the unit circle to
849 * itself. For this reason, the exact value of V does not affect the
850 * final ellipse, and we can choose V to be the identity
855 * In the end, we return the two diagonal entries of newSigma
856 * together with the two columns of U.
859 * ClampUpAxes was written by Nicolas Robidoux and Chantal Racette
860 * of Laurentian University with insightful suggestions from Anthony
861 * Thyssen and funding from the National Science and Engineering
862 * Research Council of Canada. It is distinguished from its
863 * predecessors by its efficient handling of degenerate cases.
865 * The idea of clamping up the EWA ellipse's major and minor axes so
866 * that the result contains the reconstruction kernel filter support
867 * is taken from Andreas Gustaffson's Masters thesis "Interactive
868 * Image Warping", Helsinki University of Technology, Faculty of
869 * Information Technology, 59 pages, 1993 (see Section 3.6).
871 * The use of the SVD to clamp up the singular values of the
872 * Jacobian matrix of the pullback transformation for EWA resampling
873 * is taken from the astrophysicist Craig DeForest. It is
874 * implemented in his PDL::Transform code (PDL = Perl Data
877 const double a = dux;
878 const double b = duy;
879 const double c = dvx;
880 const double d = dvy;
882 * n is the matrix Jinv * transpose(Jinv). Eigenvalues of n are the
883 * squares of the singular values of Jinv.
885 const double aa = a*a;
886 const double bb = b*b;
887 const double cc = c*c;
888 const double dd = d*d;
890 * Eigenvectors of n are left singular vectors of Jinv.
892 const double n11 = aa+bb;
893 const double n12 = a*c+b*d;
894 const double n21 = n12;
895 const double n22 = cc+dd;
896 const double det = a*d-b*c;
897 const double twice_det = det+det;
898 const double frobenius_squared = n11+n22;
899 const double discriminant =
900 (frobenius_squared+twice_det)*(frobenius_squared-twice_det);
901 const double sqrt_discriminant = sqrt(discriminant);
903 * s1 is the largest singular value of the inverse Jacobian
904 * matrix. In other words, its reciprocal is the smallest singular
905 * value of the Jacobian matrix itself.
906 * If s1 = 0, both singular values are 0, and any orthogonal pair of
907 * left and right factors produces a singular decomposition of Jinv.
910 * Initially, we only compute the squares of the singular values.
912 const double s1s1 = 0.5*(frobenius_squared+sqrt_discriminant);
914 * s2 the smallest singular value of the inverse Jacobian
915 * matrix. Its reciprocal is the largest singular value of the
916 * Jacobian matrix itself.
918 const double s2s2 = 0.5*(frobenius_squared-sqrt_discriminant);
919 const double s1s1minusn11 = s1s1-n11;
920 const double s1s1minusn22 = s1s1-n22;
922 * u1, the first column of the U factor of a singular decomposition
923 * of Jinv, is a (non-normalized) left singular vector corresponding
924 * to s1. It has entries u11 and u21. We compute u1 from the fact
925 * that it is an eigenvector of n corresponding to the eigenvalue
928 const double s1s1minusn11_squared = s1s1minusn11*s1s1minusn11;
929 const double s1s1minusn22_squared = s1s1minusn22*s1s1minusn22;
931 * The following selects the largest row of n-s1^2 I as the one
932 * which is used to find the eigenvector. If both s1^2-n11 and
933 * s1^2-n22 are zero, n-s1^2 I is the zero matrix. In that case,
934 * any vector is an eigenvector; in addition, norm below is equal to
935 * zero, and, in exact arithmetic, this is the only case in which
936 * norm = 0. So, setting u1 to the simple but arbitrary vector [1,0]
937 * if norm = 0 safely takes care of all cases.
939 const double temp_u11 =
940 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? n12 : s1s1minusn22 );
941 const double temp_u21 =
942 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? s1s1minusn11 : n21 );
943 const double norm = sqrt(temp_u11*temp_u11+temp_u21*temp_u21);
945 * Finalize the entries of first left singular vector (associated
946 * with the largest singular value).
948 const double u11 = ( (norm>0.0) ? temp_u11/norm : 1.0 );
949 const double u21 = ( (norm>0.0) ? temp_u21/norm : 0.0 );
951 * Clamp the singular values up to 1.
953 *major_mag = ( (s1s1<=1.0) ? 1.0 : sqrt(s1s1) );
954 *minor_mag = ( (s2s2<=1.0) ? 1.0 : sqrt(s2s2) );
956 * Return the unit major and minor axis direction vectors.
960 *minor_unit_x = -u21;
966 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
970 % S c a l e R e s a m p l e F i l t e r %
974 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
976 % ScaleResampleFilter() does all the calculations needed to resample an image
977 % at a specific scale, defined by two scaling vectors. This not using
978 % a orthogonal scaling, but two distorted scaling vectors, to allow the
979 % generation of a angled ellipse.
981 % As only two deritive scaling vectors are used the center of the ellipse
982 % must be the center of the lookup. That is any curvature that the
983 % distortion may produce is discounted.
985 % The input vectors are produced by either finding the derivitives of the
986 % distortion function, or the partial derivitives from a distortion mapping.
987 % They do not need to be the orthogonal dx,dy scaling vectors, but can be
988 % calculated from other derivatives. For example you could use dr,da/r
989 % polar coordinate vector scaling vectors
991 % If u,v = DistortEquation(x,y) OR u = Fu(x,y); v = Fv(x,y)
992 % Then the scaling vectors are determined from the deritives...
993 % du/dx, dv/dx and du/dy, dv/dy
994 % If the resulting scaling vectors is othogonally aligned then...
995 % dv/dx = 0 and du/dy = 0
996 % Producing an othogonally alligned ellipse in source space for the area to
999 % Note that scaling vectors are different to argument order. Argument order
1000 % is the general order the deritives are extracted from the distortion
1001 % equations, and not the scaling vectors. As such the middle two vaules
1002 % may be swapped from what you expect. Caution is advised.
1004 % WARNING: It is assumed that any SetResampleFilter() method call will
1005 % always be performed before the ScaleResampleFilter() method, so that the
1006 % size of the ellipse will match the support for the resampling filter being
1009 % The format of the ScaleResampleFilter method is:
1011 % void ScaleResampleFilter(const ResampleFilter *resample_filter,
1012 % const double dux,const double duy,const double dvx,const double dvy)
1014 % A description of each parameter follows:
1016 % o resample_filter: the resampling resample_filterrmation defining the
1017 % image being resampled
1019 % o dux,duy,dvx,dvy:
1020 % The deritives or scaling vectors defining the EWA ellipse.
1021 % NOTE: watch the order, which is based on the order deritives
1022 % are usally determined from distortion equations (see above).
1023 % The middle two values may need to be swapped if you are thinking
1024 % in terms of scaling vectors.
1027 MagickExport void ScaleResampleFilter(ResampleFilter *resample_filter,
1028 const double dux,const double duy,const double dvx,const double dvy)
1032 assert(resample_filter != (ResampleFilter *) NULL);
1033 assert(resample_filter->signature == MagickSignature);
1035 resample_filter->limit_reached = MagickFalse;
1037 /* A 'point' filter forces use of interpolation instead of area sampling */
1038 if ( resample_filter->filter == PointFilter )
1039 return; /* EWA turned off - nothing to do */
1042 (void) FormatLocaleFile(stderr, "# -----\n" );
1043 (void) FormatLocaleFile(stderr, "dux=%lf; dvx=%lf; duy=%lf; dvy=%lf;\n",
1044 dux, dvx, duy, dvy);
1047 /* Find Ellipse Coefficents such that
1048 A*u^2 + B*u*v + C*v^2 = F
1049 With u,v relative to point around which we are resampling.
1050 And the given scaling dx,dy vectors in u,v space
1051 du/dx,dv/dx and du/dy,dv/dy
1054 /* Direct conversion of derivatives into elliptical coefficients
1055 However when magnifying images, the scaling vectors will be small
1056 resulting in a ellipse that is too small to sample properly.
1057 As such we need to clamp the major/minor axis to a minumum of 1.0
1058 to prevent it getting too small.
1068 ClampUpAxes(dux,dvx,duy,dvy, &major_mag, &minor_mag,
1069 &major_x, &major_y, &minor_x, &minor_y);
1070 major_x *= major_mag; major_y *= major_mag;
1071 minor_x *= minor_mag; minor_y *= minor_mag;
1073 (void) FormatLocaleFile(stderr, "major_x=%lf; major_y=%lf; minor_x=%lf; minor_y=%lf;\n",
1074 major_x, major_y, minor_x, minor_y);
1076 A = major_y*major_y+minor_y*minor_y;
1077 B = -2.0*(major_x*major_y+minor_x*minor_y);
1078 C = major_x*major_x+minor_x*minor_x;
1079 F = major_mag*minor_mag;
1080 F *= F; /* square it */
1082 #else /* raw unclamped EWA */
1083 A = dvx*dvx+dvy*dvy;
1084 B = -2.0*(dux*dvx+duy*dvy);
1085 C = dux*dux+duy*duy;
1086 F = dux*dvy-duy*dvx;
1087 F *= F; /* square it */
1088 #endif /* EWA_CLAMP */
1092 This Paul Heckbert's "Higher Quality EWA" formula, from page 60 in his
1093 thesis, which adds a unit circle to the elliptical area so as to do both
1094 Reconstruction and Prefiltering of the pixels in the resampling. It also
1095 means it is always likely to have at least 4 pixels within the area of the
1096 ellipse, for weighted averaging. No scaling will result with F == 4.0 and
1097 a circle of radius 2.0, and F smaller than this means magnification is
1100 NOTE: This method produces a very blury result at near unity scale while
1101 producing perfect results for strong minitification and magnifications.
1103 However filter support is fixed to 2.0 (no good for Windowed Sinc filters)
1105 A = dvx*dvx+dvy*dvy+1;
1106 B = -2.0*(dux*dvx+duy*dvy);
1107 C = dux*dux+duy*duy+1;
1112 (void) FormatLocaleFile(stderr, "A=%lf; B=%lf; C=%lf; F=%lf\n", A,B,C,F);
1114 /* Figure out the various information directly about the ellipse.
1115 This information currently not needed at this time, but may be
1116 needed later for better limit determination.
1118 It is also good to have as a record for future debugging
1120 { double alpha, beta, gamma, Major, Minor;
1121 double Eccentricity, Ellipse_Area, Ellipse_Angle;
1125 gamma = sqrt(beta*beta + B*B );
1127 if ( alpha - gamma <= MagickEpsilon )
1130 Major = sqrt(2*F/(alpha - gamma));
1131 Minor = sqrt(2*F/(alpha + gamma));
1133 (void) FormatLocaleFile(stderr, "# Major=%lf; Minor=%lf\n", Major, Minor );
1135 /* other information about ellipse include... */
1136 Eccentricity = Major/Minor;
1137 Ellipse_Area = MagickPI*Major*Minor;
1138 Ellipse_Angle = atan2(B, A-C);
1140 (void) FormatLocaleFile(stderr, "# Angle=%lf Area=%lf\n",
1141 RadiansToDegrees(Ellipse_Angle), Ellipse_Area);
1145 /* If one or both of the scaling vectors is impossibly large
1146 (producing a very large raw F value), we may as well not bother
1147 doing any form of resampling since resampled area is very large.
1148 In this case some alternative means of pixel sampling, such as
1149 the average of the whole image is needed to get a reasonable
1150 result. Calculate only as needed.
1152 if ( (4*A*C - B*B) > MagickHuge ) {
1153 resample_filter->limit_reached = MagickTrue;
1157 /* Scale ellipse to match the filters support
1158 (that is, multiply F by the square of the support)
1159 Simplier to just multiply it by the support twice!
1161 F *= resample_filter->support;
1162 F *= resample_filter->support;
1164 /* Orthogonal bounds of the ellipse */
1165 resample_filter->Ulimit = sqrt(C*F/(A*C-0.25*B*B));
1166 resample_filter->Vlimit = sqrt(A*F/(A*C-0.25*B*B));
1168 /* Horizontally aligned parallelogram fitted to Ellipse */
1169 resample_filter->Uwidth = sqrt(F/A); /* Half of the parallelogram width */
1170 resample_filter->slope = -B/(2.0*A); /* Reciprocal slope of the parallelogram */
1173 (void) FormatLocaleFile(stderr, "Ulimit=%lf; Vlimit=%lf; UWidth=%lf; Slope=%lf;\n",
1174 resample_filter->Ulimit, resample_filter->Vlimit,
1175 resample_filter->Uwidth, resample_filter->slope );
1178 /* Check the absolute area of the parallelogram involved.
1179 * This limit needs more work, as it is too slow for larger images
1180 * with tiled views of the horizon.
1182 if ( (resample_filter->Uwidth * resample_filter->Vlimit)
1183 > (4.0*resample_filter->image_area)) {
1184 resample_filter->limit_reached = MagickTrue;
1188 /* Scale ellipse formula to directly index the Filter Lookup Table */
1189 { register double scale;
1191 /* scale so that F = WLUT_WIDTH; -- hardcoded */
1192 scale = (double)WLUT_WIDTH/F;
1194 /* scale so that F = resample_filter->F (support^2) */
1195 scale = resample_filter->F/F;
1197 resample_filter->A = A*scale;
1198 resample_filter->B = B*scale;
1199 resample_filter->C = C*scale;
1204 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1208 % S e t R e s a m p l e F i l t e r %
1212 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1214 % SetResampleFilter() set the resampling filter lookup table based on a
1215 % specific filter. Note that the filter is used as a radial filter not as a
1216 % two pass othogonally aligned resampling filter.
1218 % The format of the SetResampleFilter method is:
1220 % void SetResampleFilter(ResampleFilter *resample_filter,
1221 % const FilterTypes filter)
1223 % A description of each parameter follows:
1225 % o resample_filter: resampling resample_filterrmation structure
1227 % o filter: the resize filter for elliptical weighting LUT
1230 MagickExport void SetResampleFilter(ResampleFilter *resample_filter,
1231 const FilterTypes filter)
1236 assert(resample_filter != (ResampleFilter *) NULL);
1237 assert(resample_filter->signature == MagickSignature);
1239 resample_filter->do_interpolate = MagickFalse;
1240 resample_filter->filter = filter;
1242 /* Default cylindrical filter is a Cubic Keys filter */
1243 if ( filter == UndefinedFilter )
1244 resample_filter->filter = RobidouxFilter;
1246 if ( resample_filter->filter == PointFilter ) {
1247 resample_filter->do_interpolate = MagickTrue;
1248 return; /* EWA turned off - nothing more to do */
1251 resize_filter = AcquireResizeFilter(resample_filter->image,
1252 resample_filter->filter,MagickTrue,resample_filter->exception);
1253 if (resize_filter == (ResizeFilter *) NULL) {
1254 (void) ThrowMagickException(resample_filter->exception,GetMagickModule(),
1255 ModuleError, "UnableToSetFilteringValue",
1256 "Fall back to Interpolated 'Point' filter");
1257 resample_filter->filter = PointFilter;
1258 resample_filter->do_interpolate = MagickTrue;
1259 return; /* EWA turned off - nothing more to do */
1262 /* Get the practical working support for the filter,
1263 * after any API call blur factors have been accoded for.
1266 resample_filter->support = GetResizeFilterSupport(resize_filter);
1268 resample_filter->support = 2.0; /* fixed support size for HQ-EWA */
1272 /* Fill the LUT with the weights from the selected filter function */
1278 /* Scale radius so the filter LUT covers the full support range */
1279 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1280 for(Q=0; Q<WLUT_WIDTH; Q++)
1281 resample_filter->filter_lut[Q] = (double)
1282 GetResizeFilterWeight(resize_filter,sqrt((double)Q)*r_scale);
1284 /* finished with the resize filter */
1285 resize_filter = DestroyResizeFilter(resize_filter);
1288 /* save the filter and the scaled ellipse bounds needed for filter */
1289 resample_filter->filter_def = resize_filter;
1290 resample_filter->F = resample_filter->support*resample_filter->support;
1294 Adjust the scaling of the default unit circle
1295 This assumes that any real scaling changes will always
1296 take place AFTER the filter method has been initialized.
1298 ScaleResampleFilter(resample_filter, 1.0, 0.0, 0.0, 1.0);
1302 This is old code kept as a reference only. Basically it generates
1303 a Gaussian bell curve, with sigma = 0.5 if the support is 2.0
1305 Create Normal Gaussian 2D Filter Weighted Lookup Table.
1306 A normal EWA guassual lookup would use exp(Q*ALPHA)
1307 where Q = distance squared from 0.0 (center) to 1.0 (edge)
1308 and ALPHA = -4.0*ln(2.0) ==> -2.77258872223978123767
1309 The table is of length 1024, and equates to support radius of 2.0
1310 thus needs to be scaled by ALPHA*4/1024 and any blur factor squared
1312 The it comes from reference code provided by Fred Weinhaus.
1314 r_scale = -2.77258872223978123767/(WLUT_WIDTH*blur*blur);
1315 for(Q=0; Q<WLUT_WIDTH; Q++)
1316 resample_filter->filter_lut[Q] = exp((double)Q*r_scale);
1317 resample_filter->support = WLUT_WIDTH;
1321 #if defined(MAGICKCORE_OPENMP_SUPPORT)
1325 if (IsStringTrue(GetImageArtifact(resample_filter->image,
1326 "resample:verbose")) )
1333 /* Debug output of the filter weighting LUT
1334 Gnuplot the LUT data, the x scale index has been adjusted
1335 plot [0:2][-.2:1] "lut.dat" with lines
1336 The filter values should be normalized for comparision
1339 printf("# Resampling Filter LUT (%d values) for '%s' filter\n",
1340 WLUT_WIDTH, CommandOptionToMnemonic(MagickFilterOptions,
1341 resample_filter->filter) );
1343 printf("# Note: values in table are using a squared radius lookup.\n");
1344 printf("# As such its distribution is not uniform.\n");
1346 printf("# The X value is the support distance for the Y weight\n");
1347 printf("# so you can use gnuplot to plot this cylindrical filter\n");
1348 printf("# plot [0:2][-.2:1] \"lut.dat\" with lines\n");
1351 /* Scale radius so the filter LUT covers the full support range */
1352 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1353 for(Q=0; Q<WLUT_WIDTH; Q++)
1354 printf("%8.*g %.*g\n",
1355 GetMagickPrecision(),sqrt((double)Q)*r_scale,
1356 GetMagickPrecision(),resample_filter->filter_lut[Q] );
1357 printf("\n\n"); /* generate a 'break' in gnuplot if multiple outputs */
1359 /* Output the above once only for each image, and each setting
1360 (void) DeleteImageArtifact(resample_filter->image,"resample:verbose");
1363 #endif /* FILTER_LUT */
1368 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1372 % 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 %
1376 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1378 % SetResampleFilterInterpolateMethod() sets the resample filter interpolation
1381 % The format of the SetResampleFilterInterpolateMethod method is:
1383 % MagickBooleanType SetResampleFilterInterpolateMethod(
1384 % ResampleFilter *resample_filter,const InterpolateMethod method)
1386 % A description of each parameter follows:
1388 % o resample_filter: the resample filter.
1390 % o method: the interpolation method.
1393 MagickExport MagickBooleanType SetResampleFilterInterpolateMethod(
1394 ResampleFilter *resample_filter,const PixelInterpolateMethod method)
1396 assert(resample_filter != (ResampleFilter *) NULL);
1397 assert(resample_filter->signature == MagickSignature);
1398 assert(resample_filter->image != (Image *) NULL);
1399 if (resample_filter->debug != MagickFalse)
1400 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1401 resample_filter->image->filename);
1402 resample_filter->interpolate=method;
1407 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1411 % 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 %
1415 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1417 % SetResampleFilterVirtualPixelMethod() changes the virtual pixel method
1418 % associated with the specified resample filter.
1420 % The format of the SetResampleFilterVirtualPixelMethod method is:
1422 % MagickBooleanType SetResampleFilterVirtualPixelMethod(
1423 % ResampleFilter *resample_filter,const VirtualPixelMethod method)
1425 % A description of each parameter follows:
1427 % o resample_filter: the resample filter.
1429 % o method: the virtual pixel method.
1432 MagickExport MagickBooleanType SetResampleFilterVirtualPixelMethod(
1433 ResampleFilter *resample_filter,const VirtualPixelMethod method)
1435 assert(resample_filter != (ResampleFilter *) NULL);
1436 assert(resample_filter->signature == MagickSignature);
1437 assert(resample_filter->image != (Image *) NULL);
1438 if (resample_filter->debug != MagickFalse)
1439 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1440 resample_filter->image->filename);
1441 resample_filter->virtual_pixel=method;
1442 if (method != UndefinedVirtualPixelMethod)
1443 (void) SetCacheViewVirtualPixelMethod(resample_filter->view,method);