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/resource_.h"
63 #include "MagickCore/token.h"
64 #include "MagickCore/transform.h"
65 #include "MagickCore/signature-private.h"
66 #include "MagickCore/utility.h"
67 #include "MagickCore/utility-private.h"
68 #include "MagickCore/option.h"
70 EWA Resampling Options
73 /* select ONE resampling method */
74 #define EWA 1 /* Normal EWA handling - raw or clamped */
75 /* if 0 then use "High Quality EWA" */
76 #define EWA_CLAMP 1 /* EWA Clamping from Nicolas Robidoux */
78 #define FILTER_LUT 1 /* Use a LUT rather then direct filter calls */
80 /* output debugging information */
81 #define DEBUG_ELLIPSE 0 /* output ellipse info for debug */
82 #define DEBUG_HIT_MISS 0 /* output hit/miss pixels (as gnuplot commands) */
83 #define DEBUG_NO_PIXEL_HIT 0 /* Make pixels that fail to hit anything - RED */
86 #define WLUT_WIDTH 1024 /* size of the filter cache */
92 struct _ResampleFilter
106 /* Information about image being resampled */
110 PixelInterpolateMethod
119 /* processing settings needed */
128 /* current ellipitical area being resampled around center point */
131 Vlimit, Ulimit, Uwidth, slope;
134 /* LUT of weights for filtered average in elliptical area */
136 filter_lut[WLUT_WIDTH];
138 /* Use a Direct call to the filter functions */
146 /* the practical working support of the filter */
155 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
159 % A c q u i r e R e s a m p l e I n f o %
163 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
165 % AcquireResampleFilter() initializes the information resample needs do to a
166 % scaled lookup of a color from an image, using area sampling.
168 % The algorithm is based on a Elliptical Weighted Average, where the pixels
169 % found in a large elliptical area is averaged together according to a
170 % weighting (filter) function. For more details see "Fundamentals of Texture
171 % Mapping and Image Warping" a master's thesis by Paul.S.Heckbert, June 17,
172 % 1989. Available for free from, http://www.cs.cmu.edu/~ph/
174 % As EWA resampling (or any sort of resampling) can require a lot of
175 % calculations to produce a distorted scaling of the source image for each
176 % output pixel, the ResampleFilter structure generated holds that information
177 % between individual image resampling.
179 % This function will make the appropriate AcquireCacheView() calls
180 % to view the image, calling functions do not need to open a cache view.
183 % resample_filter=AcquireResampleFilter(image,exception);
184 % SetResampleFilter(resample_filter, GaussianFilter);
185 % for (y=0; y < (ssize_t) image->rows; y++) {
186 % for (x=0; x < (ssize_t) image->columns; x++) {
188 % ScaleResampleFilter(resample_filter, ... scaling vectors ...);
189 % (void) ResamplePixelColor(resample_filter,u,v,&pixel);
190 % ... assign resampled pixel value ...
193 % DestroyResampleFilter(resample_filter);
195 % The format of the AcquireResampleFilter method is:
197 % ResampleFilter *AcquireResampleFilter(const Image *image,
198 % ExceptionInfo *exception)
200 % A description of each parameter follows:
202 % o image: the image.
204 % o exception: return any errors or warnings in this structure.
207 MagickExport ResampleFilter *AcquireResampleFilter(const Image *image,
208 ExceptionInfo *exception)
210 register ResampleFilter
213 assert(image != (Image *) NULL);
214 assert(image->signature == MagickSignature);
215 if (image->debug != MagickFalse)
216 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
217 assert(exception != (ExceptionInfo *) NULL);
218 assert(exception->signature == MagickSignature);
220 resample_filter=(ResampleFilter *) AcquireMagickMemory(
221 sizeof(*resample_filter));
222 if (resample_filter == (ResampleFilter *) NULL)
223 ThrowFatalException(ResourceLimitFatalError,"MemoryAllocationFailed");
224 (void) ResetMagickMemory(resample_filter,0,sizeof(*resample_filter));
226 resample_filter->exception=exception;
227 resample_filter->image=ReferenceImage((Image *) image);
228 resample_filter->view=AcquireVirtualCacheView(resample_filter->image,exception);
230 resample_filter->debug=IsEventLogging();
231 resample_filter->signature=MagickSignature;
233 resample_filter->image_area=(ssize_t) (image->columns*image->rows);
234 resample_filter->average_defined = MagickFalse;
236 /* initialise the resampling filter settings */
237 SetResampleFilter(resample_filter, image->filter);
238 (void) SetResampleFilterInterpolateMethod(resample_filter,image->interpolate);
239 (void) SetResampleFilterVirtualPixelMethod(resample_filter,
240 GetImageVirtualPixelMethod(image));
241 return(resample_filter);
245 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
249 % D e s t r o y R e s a m p l e I n f o %
253 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
255 % DestroyResampleFilter() finalizes and cleans up the resampling
256 % resample_filter as returned by AcquireResampleFilter(), freeing any memory
257 % or other information as needed.
259 % The format of the DestroyResampleFilter method is:
261 % ResampleFilter *DestroyResampleFilter(ResampleFilter *resample_filter)
263 % A description of each parameter follows:
265 % o resample_filter: resampling information structure
268 MagickExport ResampleFilter *DestroyResampleFilter(
269 ResampleFilter *resample_filter)
271 assert(resample_filter != (ResampleFilter *) NULL);
272 assert(resample_filter->signature == MagickSignature);
273 assert(resample_filter->image != (Image *) NULL);
274 if (resample_filter->debug != MagickFalse)
275 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
276 resample_filter->image->filename);
277 resample_filter->view=DestroyCacheView(resample_filter->view);
278 resample_filter->image=DestroyImage(resample_filter->image);
280 resample_filter->filter_def=DestroyResizeFilter(resample_filter->filter_def);
282 resample_filter->signature=(~MagickSignature);
283 resample_filter=(ResampleFilter *) RelinquishMagickMemory(resample_filter);
284 return(resample_filter);
288 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
292 % R e s a m p l e P i x e l C o l o r %
296 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
298 % ResamplePixelColor() samples the pixel values surrounding the location
299 % given using an elliptical weighted average, at the scale previously
300 % calculated, and in the most efficent manner possible for the
301 % VirtualPixelMethod setting.
303 % The format of the ResamplePixelColor method is:
305 % MagickBooleanType ResamplePixelColor(ResampleFilter *resample_filter,
306 % const double u0,const double v0,PixelInfo *pixel,
307 % ExceptionInfo *exception)
309 % A description of each parameter follows:
311 % o resample_filter: the resample filter.
313 % o u0,v0: A double representing the center of the area to resample,
314 % The distortion transformed transformed x,y coordinate.
316 % o pixel: the resampled pixel is returned here.
318 % o exception: return any errors or warnings in this structure.
321 MagickExport MagickBooleanType ResamplePixelColor(
322 ResampleFilter *resample_filter,const double u0,const double v0,
323 PixelInfo *pixel,ExceptionInfo *exception)
328 ssize_t u,v, v1, v2, uw, hit;
331 double divisor_c,divisor_m;
332 register double weight;
333 register const Quantum *pixels;
334 assert(resample_filter != (ResampleFilter *) NULL);
335 assert(resample_filter->signature == MagickSignature);
338 /* GetPixelInfo(resample_filter->image,pixel); */
339 if ( resample_filter->do_interpolate ) {
340 status=InterpolatePixelInfo(resample_filter->image,resample_filter->view,
341 resample_filter->interpolate,u0,v0,pixel,resample_filter->exception);
346 (void) FormatLocaleFile(stderr, "u0=%lf; v0=%lf;\n", u0, v0);
350 Does resample area Miss the image?
351 And is that area a simple solid color - then return that color
354 switch ( resample_filter->virtual_pixel ) {
355 case BackgroundVirtualPixelMethod:
356 case TransparentVirtualPixelMethod:
357 case BlackVirtualPixelMethod:
358 case GrayVirtualPixelMethod:
359 case WhiteVirtualPixelMethod:
360 case MaskVirtualPixelMethod:
361 if ( resample_filter->limit_reached
362 || u0 + resample_filter->Ulimit < 0.0
363 || u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
364 || v0 + resample_filter->Vlimit < 0.0
365 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows
370 case UndefinedVirtualPixelMethod:
371 case EdgeVirtualPixelMethod:
372 if ( ( u0 + resample_filter->Ulimit < 0.0 && v0 + resample_filter->Vlimit < 0.0 )
373 || ( u0 + resample_filter->Ulimit < 0.0
374 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows )
375 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
376 && v0 + resample_filter->Vlimit < 0.0 )
377 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
378 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows )
382 case HorizontalTileVirtualPixelMethod:
383 if ( v0 + resample_filter->Vlimit < 0.0
384 || v0 - resample_filter->Vlimit > (double) resample_filter->image->rows
386 hit++; /* outside the horizontally tiled images. */
388 case VerticalTileVirtualPixelMethod:
389 if ( u0 + resample_filter->Ulimit < 0.0
390 || u0 - resample_filter->Ulimit > (double) resample_filter->image->columns
392 hit++; /* outside the vertically tiled images. */
394 case DitherVirtualPixelMethod:
395 if ( ( u0 + resample_filter->Ulimit < -32.0 && v0 + resample_filter->Vlimit < -32.0 )
396 || ( u0 + resample_filter->Ulimit < -32.0
397 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows+32.0 )
398 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+32.0
399 && v0 + resample_filter->Vlimit < -32.0 )
400 || ( u0 - resample_filter->Ulimit > (double) resample_filter->image->columns+32.0
401 && v0 - resample_filter->Vlimit > (double) resample_filter->image->rows+32.0 )
405 case TileVirtualPixelMethod:
406 case MirrorVirtualPixelMethod:
407 case RandomVirtualPixelMethod:
408 case HorizontalTileEdgeVirtualPixelMethod:
409 case VerticalTileEdgeVirtualPixelMethod:
410 case CheckerTileVirtualPixelMethod:
411 /* resampling of area is always needed - no VP limits */
415 /* whole area is a solid color -- just return that color */
416 status=InterpolatePixelInfo(resample_filter->image,
417 resample_filter->view,IntegerInterpolatePixel,u0,v0,pixel,
418 resample_filter->exception);
423 Scaling limits reached, return an 'averaged' result.
425 if ( resample_filter->limit_reached ) {
426 switch ( resample_filter->virtual_pixel ) {
427 /* This is always handled by the above, so no need.
428 case BackgroundVirtualPixelMethod:
429 case ConstantVirtualPixelMethod:
430 case TransparentVirtualPixelMethod:
431 case GrayVirtualPixelMethod,
432 case WhiteVirtualPixelMethod
433 case MaskVirtualPixelMethod:
435 case UndefinedVirtualPixelMethod:
436 case EdgeVirtualPixelMethod:
437 case DitherVirtualPixelMethod:
438 case HorizontalTileEdgeVirtualPixelMethod:
439 case VerticalTileEdgeVirtualPixelMethod:
440 /* We need an average edge pixel, from the correct edge!
441 How should I calculate an average edge color?
442 Just returning an averaged neighbourhood,
443 works well in general, but falls down for TileEdge methods.
444 This needs to be done properly!!!!!!
446 status=InterpolatePixelInfo(resample_filter->image,
447 resample_filter->view,AverageInterpolatePixel,u0,v0,pixel,
448 resample_filter->exception);
450 case HorizontalTileVirtualPixelMethod:
451 case VerticalTileVirtualPixelMethod:
452 /* just return the background pixel - Is there more direct way? */
453 status=InterpolatePixelInfo(resample_filter->image,
454 resample_filter->view,IntegerInterpolatePixel,-1.0,-1.0,pixel,
455 resample_filter->exception);
457 case TileVirtualPixelMethod:
458 case MirrorVirtualPixelMethod:
459 case RandomVirtualPixelMethod:
460 case CheckerTileVirtualPixelMethod:
462 /* generate a average color of the WHOLE image */
463 if ( resample_filter->average_defined == MagickFalse ) {
470 GetPixelInfo(resample_filter->image,(PixelInfo *)
471 &resample_filter->average_pixel);
472 resample_filter->average_defined=MagickTrue;
474 /* Try to get an averaged pixel color of whole image */
475 average_image=ResizeImage(resample_filter->image,1,1,BoxFilter,
476 resample_filter->exception);
477 if (average_image == (Image *) NULL)
479 *pixel=resample_filter->average_pixel; /* FAILED */
482 average_view=AcquireVirtualCacheView(average_image,exception);
483 pixels=GetCacheViewVirtualPixels(average_view,0,0,1,1,
484 resample_filter->exception);
485 if (pixels == (const Quantum *) NULL) {
486 average_view=DestroyCacheView(average_view);
487 average_image=DestroyImage(average_image);
488 *pixel=resample_filter->average_pixel; /* FAILED */
491 GetPixelInfoPixel(resample_filter->image,pixels,
492 &(resample_filter->average_pixel));
493 average_view=DestroyCacheView(average_view);
494 average_image=DestroyImage(average_image);
496 if ( resample_filter->virtual_pixel == CheckerTileVirtualPixelMethod )
498 /* CheckerTile is a alpha blend of the image's average pixel
499 color and the current background color */
501 /* image's average pixel color */
502 weight = QuantumScale*((double)
503 resample_filter->average_pixel.alpha);
504 resample_filter->average_pixel.red *= weight;
505 resample_filter->average_pixel.green *= weight;
506 resample_filter->average_pixel.blue *= weight;
509 /* background color */
510 weight = QuantumScale*((double)
511 resample_filter->image->background_color.alpha);
512 resample_filter->average_pixel.red +=
513 weight*resample_filter->image->background_color.red;
514 resample_filter->average_pixel.green +=
515 weight*resample_filter->image->background_color.green;
516 resample_filter->average_pixel.blue +=
517 weight*resample_filter->image->background_color.blue;
518 resample_filter->average_pixel.alpha +=
519 resample_filter->image->background_color.alpha;
523 resample_filter->average_pixel.red /= divisor_c;
524 resample_filter->average_pixel.green /= divisor_c;
525 resample_filter->average_pixel.blue /= divisor_c;
526 resample_filter->average_pixel.alpha /= 2; /* 50% blend */
530 *pixel=resample_filter->average_pixel;
537 Initialize weighted average data collection
542 pixel->red = pixel->green = pixel->blue = 0.0;
543 if (pixel->colorspace == CMYKColorspace)
545 if (pixel->alpha_trait == BlendPixelTrait)
549 Determine the parellelogram bounding box fitted to the ellipse
550 centered at u0,v0. This area is bounding by the lines...
552 v1 = (ssize_t)ceil(v0 - resample_filter->Vlimit); /* range of scan lines */
553 v2 = (ssize_t)floor(v0 + resample_filter->Vlimit);
555 /* scan line start and width accross the parallelogram */
556 u1 = u0 + (v1-v0)*resample_filter->slope - resample_filter->Uwidth;
557 uw = (ssize_t)(2.0*resample_filter->Uwidth)+1;
560 (void) FormatLocaleFile(stderr, "v1=%ld; v2=%ld\n", (long)v1, (long)v2);
561 (void) FormatLocaleFile(stderr, "u1=%ld; uw=%ld\n", (long)u1, (long)uw);
563 # define DEBUG_HIT_MISS 0 /* only valid if DEBUG_ELLIPSE is enabled */
567 Do weighted resampling of all pixels, within the scaled ellipse,
568 bound by a Parellelogram fitted to the ellipse.
570 DDQ = 2*resample_filter->A;
571 for( v=v1; v<=v2; v++ ) {
573 long uu = ceil(u1); /* actual pixel location (for debug only) */
574 (void) FormatLocaleFile(stderr, "# scan line from pixel %ld, %ld\n", (long)uu, (long)v);
576 u = (ssize_t)ceil(u1); /* first pixel in scanline */
577 u1 += resample_filter->slope; /* start of next scan line */
580 /* location of this first pixel, relative to u0,v0 */
584 /* Q = ellipse quotent ( if Q<F then pixel is inside ellipse) */
585 Q = (resample_filter->A*U + resample_filter->B*V)*U + resample_filter->C*V*V;
586 DQ = resample_filter->A*(2.0*U+1) + resample_filter->B*V;
588 /* get the scanline of pixels for this v */
589 pixels=GetCacheViewVirtualPixels(resample_filter->view,u,v,(size_t) uw,
590 1,resample_filter->exception);
591 if (pixels == (const Quantum *) NULL)
594 /* count up the weighted pixel colors */
595 for( u=0; u<uw; u++ ) {
597 /* Note that the ellipse has been pre-scaled so F = WLUT_WIDTH */
598 if ( Q < (double)WLUT_WIDTH ) {
599 weight = resample_filter->filter_lut[(int)Q];
601 /* Note that the ellipse has been pre-scaled so F = support^2 */
602 if ( Q < (double)resample_filter->F ) {
603 weight = GetResizeFilterWeight(resample_filter->filter_def,
604 sqrt(Q)); /* a SquareRoot! Arrggghhhhh... */
607 pixel->alpha += weight*GetPixelAlpha(resample_filter->image,pixels);
610 if (pixel->alpha_trait == BlendPixelTrait)
611 weight *= QuantumScale*((double) GetPixelAlpha(resample_filter->image,pixels));
612 pixel->red += weight*GetPixelRed(resample_filter->image,pixels);
613 pixel->green += weight*GetPixelGreen(resample_filter->image,pixels);
614 pixel->blue += weight*GetPixelBlue(resample_filter->image,pixels);
615 if (pixel->colorspace == CMYKColorspace)
616 pixel->black += weight*GetPixelBlack(resample_filter->image,pixels);
621 /* mark the pixel according to hit/miss of the ellipse */
622 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
623 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
624 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 3\n",
625 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
627 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
628 (long)uu-.1,(double)v-.1,(long)uu+.1,(long)v+.1);
629 (void) FormatLocaleFile(stderr, "set arrow from %lf,%lf to %lf,%lf nohead ls 1\n",
630 (long)uu+.1,(double)v-.1,(long)uu-.1,(long)v+.1);
636 pixels+=GetPixelChannels(resample_filter->image);
642 (void) FormatLocaleFile(stderr, "Hit=%ld; Total=%ld;\n", (long)hit, (long)uw*(v2-v1) );
646 Result sanity check -- this should NOT happen
648 if ( hit == 0 || divisor_m <= MagickEpsilon || divisor_c <= MagickEpsilon ) {
649 /* not enough pixels, or bad weighting in resampling,
650 resort to direct interpolation */
651 #if DEBUG_NO_PIXEL_HIT
652 pixel->alpha = pixel->red = pixel->green = pixel->blue = 0;
653 pixel->red = QuantumRange; /* show pixels for which EWA fails */
655 status=InterpolatePixelInfo(resample_filter->image,
656 resample_filter->view,resample_filter->interpolate,u0,v0,pixel,
657 resample_filter->exception);
663 Finialize results of resampling
665 divisor_m = 1.0/divisor_m;
666 pixel->alpha = (double) ClampToQuantum(divisor_m*pixel->alpha);
667 divisor_c = 1.0/divisor_c;
668 pixel->red = (double) ClampToQuantum(divisor_c*pixel->red);
669 pixel->green = (double) ClampToQuantum(divisor_c*pixel->green);
670 pixel->blue = (double) ClampToQuantum(divisor_c*pixel->blue);
671 if (pixel->colorspace == CMYKColorspace)
672 pixel->black = (double) ClampToQuantum(divisor_c*pixel->black);
678 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
682 - C l a m p U p A x e s %
686 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
688 % ClampUpAxes() function converts the input vectors into a major and
689 % minor axis unit vectors, and their magnitude. This allows us to
690 % ensure that the ellipse generated is never smaller than the unit
691 % circle and thus never too small for use in EWA resampling.
693 % This purely mathematical 'magic' was provided by Professor Nicolas
694 % Robidoux and his Masters student Chantal Racette.
696 % Reference: "We Recommend Singular Value Decomposition", David Austin
697 % http://www.ams.org/samplings/feature-column/fcarc-svd
699 % By generating major and minor axis vectors, we can actually use the
700 % ellipse in its "canonical form", by remapping the dx,dy of the
701 % sampled point into distances along the major and minor axis unit
704 % Reference: http://en.wikipedia.org/wiki/Ellipse#Canonical_form
706 static inline void ClampUpAxes(const double dux,
712 double *major_unit_x,
713 double *major_unit_y,
714 double *minor_unit_x,
715 double *minor_unit_y)
718 * ClampUpAxes takes an input 2x2 matrix
720 * [ a b ] = [ dux duy ]
721 * [ c d ] = [ dvx dvy ]
723 * and computes from it the major and minor axis vectors [major_x,
724 * major_y] and [minor_x,minor_y] of the smallest ellipse containing
725 * both the unit disk and the ellipse which is the image of the unit
726 * disk by the linear transformation
728 * [ dux duy ] [S] = [s]
729 * [ dvx dvy ] [T] = [t]
731 * (The vector [S,T] is the difference between a position in output
732 * space and [X,Y]; the vector [s,t] is the difference between a
733 * position in input space and [x,y].)
738 * major_mag is the half-length of the major axis of the "new"
741 * minor_mag is the half-length of the minor axis of the "new"
744 * major_unit_x is the x-coordinate of the major axis direction vector
745 * of both the "old" and "new" ellipses.
747 * major_unit_y is the y-coordinate of the major axis direction vector.
749 * minor_unit_x is the x-coordinate of the minor axis direction vector.
751 * minor_unit_y is the y-coordinate of the minor axis direction vector.
753 * Unit vectors are useful for computing projections, in particular,
754 * to compute the distance between a point in output space and the
755 * center of a unit disk in output space, using the position of the
756 * corresponding point [s,t] in input space. Following the clamping,
757 * the square of this distance is
759 * ( ( s * major_unit_x + t * major_unit_y ) / major_mag )^2
761 * ( ( s * minor_unit_x + t * minor_unit_y ) / minor_mag )^2
763 * If such distances will be computed for many [s,t]'s, it makes
764 * sense to actually compute the reciprocal of major_mag and
765 * minor_mag and multiply them by the above unit lengths.
767 * Now, if you want to modify the input pair of tangent vectors so
768 * that it defines the modified ellipse, all you have to do is set
770 * newdux = major_mag * major_unit_x
771 * newdvx = major_mag * major_unit_y
772 * newduy = minor_mag * minor_unit_x = minor_mag * -major_unit_y
773 * newdvy = minor_mag * minor_unit_y = minor_mag * major_unit_x
775 * and use these tangent vectors as if they were the original ones.
776 * Usually, this is a drastic change in the tangent vectors even if
777 * the singular values are not clamped; for example, the minor axis
778 * vector always points in a direction which is 90 degrees
779 * counterclockwise from the direction of the major axis vector.
784 * GOAL: Fix things so that the pullback, in input space, of a disk
785 * of radius r in output space is an ellipse which contains, at
786 * least, a disc of radius r. (Make this hold for any r>0.)
788 * ESSENCE OF THE METHOD: Compute the product of the first two
789 * factors of an SVD of the linear transformation defining the
790 * ellipse and make sure that both its columns have norm at least 1.
791 * Because rotations and reflexions map disks to themselves, it is
792 * not necessary to compute the third (rightmost) factor of the SVD.
794 * DETAILS: Find the singular values and (unit) left singular
795 * vectors of Jinv, clampling up the singular values to 1, and
796 * multiply the unit left singular vectors by the new singular
797 * values in order to get the minor and major ellipse axis vectors.
799 * Image resampling context:
801 * The Jacobian matrix of the transformation at the output point
802 * under consideration is defined as follows:
804 * Consider the transformation (x,y) -> (X,Y) from input locations
805 * to output locations. (Anthony Thyssen, elsewhere in resample.c,
806 * uses the notation (u,v) -> (x,y).)
808 * The Jacobian matrix of the transformation at (x,y) is equal to
810 * J = [ A, B ] = [ dX/dx, dX/dy ]
811 * [ C, D ] [ dY/dx, dY/dy ]
813 * that is, the vector [A,C] is the tangent vector corresponding to
814 * input changes in the horizontal direction, and the vector [B,D]
815 * is the tangent vector corresponding to input changes in the
816 * vertical direction.
818 * In the context of resampling, it is natural to use the inverse
819 * Jacobian matrix Jinv because resampling is generally performed by
820 * pulling pixel locations in the output image back to locations in
821 * the input image. Jinv is
823 * Jinv = [ a, b ] = [ dx/dX, dx/dY ]
824 * [ c, d ] [ dy/dX, dy/dY ]
826 * Note: Jinv can be computed from J with the following matrix
829 * Jinv = 1/(A*D-B*C) [ D, -B ]
832 * What we do is modify Jinv so that it generates an ellipse which
833 * is as close as possible to the original but which contains the
834 * unit disk. This can be accomplished as follows:
840 * be an SVD decomposition of Jinv. (The SVD is not unique, but the
841 * final ellipse does not depend on the particular SVD.)
843 * We could clamp up the entries of the diagonal matrix Sigma so
844 * that they are at least 1, and then set
846 * Jinv = U newSigma V^T.
848 * However, we do not need to compute V for the following reason:
849 * V^T is an orthogonal matrix (that is, it represents a combination
850 * of rotations and reflexions) so that it maps the unit circle to
851 * itself. For this reason, the exact value of V does not affect the
852 * final ellipse, and we can choose V to be the identity
857 * In the end, we return the two diagonal entries of newSigma
858 * together with the two columns of U.
861 * ClampUpAxes was written by Nicolas Robidoux and Chantal Racette
862 * of Laurentian University with insightful suggestions from Anthony
863 * Thyssen and funding from the National Science and Engineering
864 * Research Council of Canada. It is distinguished from its
865 * predecessors by its efficient handling of degenerate cases.
867 * The idea of clamping up the EWA ellipse's major and minor axes so
868 * that the result contains the reconstruction kernel filter support
869 * is taken from Andreas Gustaffson's Masters thesis "Interactive
870 * Image Warping", Helsinki University of Technology, Faculty of
871 * Information Technology, 59 pages, 1993 (see Section 3.6).
873 * The use of the SVD to clamp up the singular values of the
874 * Jacobian matrix of the pullback transformation for EWA resampling
875 * is taken from the astrophysicist Craig DeForest. It is
876 * implemented in his PDL::Transform code (PDL = Perl Data
879 const double a = dux;
880 const double b = duy;
881 const double c = dvx;
882 const double d = dvy;
884 * n is the matrix Jinv * transpose(Jinv). Eigenvalues of n are the
885 * squares of the singular values of Jinv.
887 const double aa = a*a;
888 const double bb = b*b;
889 const double cc = c*c;
890 const double dd = d*d;
892 * Eigenvectors of n are left singular vectors of Jinv.
894 const double n11 = aa+bb;
895 const double n12 = a*c+b*d;
896 const double n21 = n12;
897 const double n22 = cc+dd;
898 const double det = a*d-b*c;
899 const double twice_det = det+det;
900 const double frobenius_squared = n11+n22;
901 const double discriminant =
902 (frobenius_squared+twice_det)*(frobenius_squared-twice_det);
903 const double sqrt_discriminant = sqrt(discriminant);
905 * s1 is the largest singular value of the inverse Jacobian
906 * matrix. In other words, its reciprocal is the smallest singular
907 * value of the Jacobian matrix itself.
908 * If s1 = 0, both singular values are 0, and any orthogonal pair of
909 * left and right factors produces a singular decomposition of Jinv.
912 * Initially, we only compute the squares of the singular values.
914 const double s1s1 = 0.5*(frobenius_squared+sqrt_discriminant);
916 * s2 the smallest singular value of the inverse Jacobian
917 * matrix. Its reciprocal is the largest singular value of the
918 * Jacobian matrix itself.
920 const double s2s2 = 0.5*(frobenius_squared-sqrt_discriminant);
921 const double s1s1minusn11 = s1s1-n11;
922 const double s1s1minusn22 = s1s1-n22;
924 * u1, the first column of the U factor of a singular decomposition
925 * of Jinv, is a (non-normalized) left singular vector corresponding
926 * to s1. It has entries u11 and u21. We compute u1 from the fact
927 * that it is an eigenvector of n corresponding to the eigenvalue
930 const double s1s1minusn11_squared = s1s1minusn11*s1s1minusn11;
931 const double s1s1minusn22_squared = s1s1minusn22*s1s1minusn22;
933 * The following selects the largest row of n-s1^2 I as the one
934 * which is used to find the eigenvector. If both s1^2-n11 and
935 * s1^2-n22 are zero, n-s1^2 I is the zero matrix. In that case,
936 * any vector is an eigenvector; in addition, norm below is equal to
937 * zero, and, in exact arithmetic, this is the only case in which
938 * norm = 0. So, setting u1 to the simple but arbitrary vector [1,0]
939 * if norm = 0 safely takes care of all cases.
941 const double temp_u11 =
942 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? n12 : s1s1minusn22 );
943 const double temp_u21 =
944 ( (s1s1minusn11_squared>=s1s1minusn22_squared) ? s1s1minusn11 : n21 );
945 const double norm = sqrt(temp_u11*temp_u11+temp_u21*temp_u21);
947 * Finalize the entries of first left singular vector (associated
948 * with the largest singular value).
950 const double u11 = ( (norm>0.0) ? temp_u11/norm : 1.0 );
951 const double u21 = ( (norm>0.0) ? temp_u21/norm : 0.0 );
953 * Clamp the singular values up to 1.
955 *major_mag = ( (s1s1<=1.0) ? 1.0 : sqrt(s1s1) );
956 *minor_mag = ( (s2s2<=1.0) ? 1.0 : sqrt(s2s2) );
958 * Return the unit major and minor axis direction vectors.
962 *minor_unit_x = -u21;
968 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
972 % S c a l e R e s a m p l e F i l t e r %
976 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
978 % ScaleResampleFilter() does all the calculations needed to resample an image
979 % at a specific scale, defined by two scaling vectors. This not using
980 % a orthogonal scaling, but two distorted scaling vectors, to allow the
981 % generation of a angled ellipse.
983 % As only two deritive scaling vectors are used the center of the ellipse
984 % must be the center of the lookup. That is any curvature that the
985 % distortion may produce is discounted.
987 % The input vectors are produced by either finding the derivitives of the
988 % distortion function, or the partial derivitives from a distortion mapping.
989 % They do not need to be the orthogonal dx,dy scaling vectors, but can be
990 % calculated from other derivatives. For example you could use dr,da/r
991 % polar coordinate vector scaling vectors
993 % If u,v = DistortEquation(x,y) OR u = Fu(x,y); v = Fv(x,y)
994 % Then the scaling vectors are determined from the deritives...
995 % du/dx, dv/dx and du/dy, dv/dy
996 % If the resulting scaling vectors is othogonally aligned then...
997 % dv/dx = 0 and du/dy = 0
998 % Producing an othogonally alligned ellipse in source space for the area to
1001 % Note that scaling vectors are different to argument order. Argument order
1002 % is the general order the deritives are extracted from the distortion
1003 % equations, and not the scaling vectors. As such the middle two vaules
1004 % may be swapped from what you expect. Caution is advised.
1006 % WARNING: It is assumed that any SetResampleFilter() method call will
1007 % always be performed before the ScaleResampleFilter() method, so that the
1008 % size of the ellipse will match the support for the resampling filter being
1011 % The format of the ScaleResampleFilter method is:
1013 % void ScaleResampleFilter(const ResampleFilter *resample_filter,
1014 % const double dux,const double duy,const double dvx,const double dvy)
1016 % A description of each parameter follows:
1018 % o resample_filter: the resampling resample_filterrmation defining the
1019 % image being resampled
1021 % o dux,duy,dvx,dvy:
1022 % The deritives or scaling vectors defining the EWA ellipse.
1023 % NOTE: watch the order, which is based on the order deritives
1024 % are usally determined from distortion equations (see above).
1025 % The middle two values may need to be swapped if you are thinking
1026 % in terms of scaling vectors.
1029 MagickExport void ScaleResampleFilter(ResampleFilter *resample_filter,
1030 const double dux,const double duy,const double dvx,const double dvy)
1034 assert(resample_filter != (ResampleFilter *) NULL);
1035 assert(resample_filter->signature == MagickSignature);
1037 resample_filter->limit_reached = MagickFalse;
1039 /* A 'point' filter forces use of interpolation instead of area sampling */
1040 if ( resample_filter->filter == PointFilter )
1041 return; /* EWA turned off - nothing to do */
1044 (void) FormatLocaleFile(stderr, "# -----\n" );
1045 (void) FormatLocaleFile(stderr, "dux=%lf; dvx=%lf; duy=%lf; dvy=%lf;\n",
1046 dux, dvx, duy, dvy);
1049 /* Find Ellipse Coefficents such that
1050 A*u^2 + B*u*v + C*v^2 = F
1051 With u,v relative to point around which we are resampling.
1052 And the given scaling dx,dy vectors in u,v space
1053 du/dx,dv/dx and du/dy,dv/dy
1056 /* Direct conversion of derivatives into elliptical coefficients
1057 However when magnifying images, the scaling vectors will be small
1058 resulting in a ellipse that is too small to sample properly.
1059 As such we need to clamp the major/minor axis to a minumum of 1.0
1060 to prevent it getting too small.
1070 ClampUpAxes(dux,dvx,duy,dvy, &major_mag, &minor_mag,
1071 &major_x, &major_y, &minor_x, &minor_y);
1072 major_x *= major_mag; major_y *= major_mag;
1073 minor_x *= minor_mag; minor_y *= minor_mag;
1075 (void) FormatLocaleFile(stderr, "major_x=%lf; major_y=%lf; minor_x=%lf; minor_y=%lf;\n",
1076 major_x, major_y, minor_x, minor_y);
1078 A = major_y*major_y+minor_y*minor_y;
1079 B = -2.0*(major_x*major_y+minor_x*minor_y);
1080 C = major_x*major_x+minor_x*minor_x;
1081 F = major_mag*minor_mag;
1082 F *= F; /* square it */
1084 #else /* raw unclamped EWA */
1085 A = dvx*dvx+dvy*dvy;
1086 B = -2.0*(dux*dvx+duy*dvy);
1087 C = dux*dux+duy*duy;
1088 F = dux*dvy-duy*dvx;
1089 F *= F; /* square it */
1090 #endif /* EWA_CLAMP */
1094 This Paul Heckbert's "Higher Quality EWA" formula, from page 60 in his
1095 thesis, which adds a unit circle to the elliptical area so as to do both
1096 Reconstruction and Prefiltering of the pixels in the resampling. It also
1097 means it is always likely to have at least 4 pixels within the area of the
1098 ellipse, for weighted averaging. No scaling will result with F == 4.0 and
1099 a circle of radius 2.0, and F smaller than this means magnification is
1102 NOTE: This method produces a very blury result at near unity scale while
1103 producing perfect results for strong minitification and magnifications.
1105 However filter support is fixed to 2.0 (no good for Windowed Sinc filters)
1107 A = dvx*dvx+dvy*dvy+1;
1108 B = -2.0*(dux*dvx+duy*dvy);
1109 C = dux*dux+duy*duy+1;
1114 (void) FormatLocaleFile(stderr, "A=%lf; B=%lf; C=%lf; F=%lf\n", A,B,C,F);
1116 /* Figure out the various information directly about the ellipse.
1117 This information currently not needed at this time, but may be
1118 needed later for better limit determination.
1120 It is also good to have as a record for future debugging
1122 { double alpha, beta, gamma, Major, Minor;
1123 double Eccentricity, Ellipse_Area, Ellipse_Angle;
1127 gamma = sqrt(beta*beta + B*B );
1129 if ( alpha - gamma <= MagickEpsilon )
1132 Major = sqrt(2*F/(alpha - gamma));
1133 Minor = sqrt(2*F/(alpha + gamma));
1135 (void) FormatLocaleFile(stderr, "# Major=%lf; Minor=%lf\n", Major, Minor );
1137 /* other information about ellipse include... */
1138 Eccentricity = Major/Minor;
1139 Ellipse_Area = MagickPI*Major*Minor;
1140 Ellipse_Angle = atan2(B, A-C);
1142 (void) FormatLocaleFile(stderr, "# Angle=%lf Area=%lf\n",
1143 RadiansToDegrees(Ellipse_Angle), Ellipse_Area);
1147 /* If one or both of the scaling vectors is impossibly large
1148 (producing a very large raw F value), we may as well not bother
1149 doing any form of resampling since resampled area is very large.
1150 In this case some alternative means of pixel sampling, such as
1151 the average of the whole image is needed to get a reasonable
1152 result. Calculate only as needed.
1154 if ( (4*A*C - B*B) > MagickHuge ) {
1155 resample_filter->limit_reached = MagickTrue;
1159 /* Scale ellipse to match the filters support
1160 (that is, multiply F by the square of the support)
1161 Simplier to just multiply it by the support twice!
1163 F *= resample_filter->support;
1164 F *= resample_filter->support;
1166 /* Orthogonal bounds of the ellipse */
1167 resample_filter->Ulimit = sqrt(C*F/(A*C-0.25*B*B));
1168 resample_filter->Vlimit = sqrt(A*F/(A*C-0.25*B*B));
1170 /* Horizontally aligned parallelogram fitted to Ellipse */
1171 resample_filter->Uwidth = sqrt(F/A); /* Half of the parallelogram width */
1172 resample_filter->slope = -B/(2.0*A); /* Reciprocal slope of the parallelogram */
1175 (void) FormatLocaleFile(stderr, "Ulimit=%lf; Vlimit=%lf; UWidth=%lf; Slope=%lf;\n",
1176 resample_filter->Ulimit, resample_filter->Vlimit,
1177 resample_filter->Uwidth, resample_filter->slope );
1180 /* Check the absolute area of the parallelogram involved.
1181 * This limit needs more work, as it is too slow for larger images
1182 * with tiled views of the horizon.
1184 if ( (resample_filter->Uwidth * resample_filter->Vlimit)
1185 > (4.0*resample_filter->image_area)) {
1186 resample_filter->limit_reached = MagickTrue;
1190 /* Scale ellipse formula to directly index the Filter Lookup Table */
1191 { register double scale;
1193 /* scale so that F = WLUT_WIDTH; -- hardcoded */
1194 scale = (double)WLUT_WIDTH/F;
1196 /* scale so that F = resample_filter->F (support^2) */
1197 scale = resample_filter->F/F;
1199 resample_filter->A = A*scale;
1200 resample_filter->B = B*scale;
1201 resample_filter->C = C*scale;
1206 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1210 % S e t R e s a m p l e F i l t e r %
1214 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1216 % SetResampleFilter() set the resampling filter lookup table based on a
1217 % specific filter. Note that the filter is used as a radial filter not as a
1218 % two pass othogonally aligned resampling filter.
1220 % The format of the SetResampleFilter method is:
1222 % void SetResampleFilter(ResampleFilter *resample_filter,
1223 % const FilterTypes filter)
1225 % A description of each parameter follows:
1227 % o resample_filter: resampling resample_filterrmation structure
1229 % o filter: the resize filter for elliptical weighting LUT
1232 MagickExport void SetResampleFilter(ResampleFilter *resample_filter,
1233 const FilterTypes filter)
1238 assert(resample_filter != (ResampleFilter *) NULL);
1239 assert(resample_filter->signature == MagickSignature);
1241 resample_filter->do_interpolate = MagickFalse;
1242 resample_filter->filter = filter;
1244 /* Default cylindrical filter is a Cubic Keys filter */
1245 if ( filter == UndefinedFilter )
1246 resample_filter->filter = RobidouxFilter;
1248 if ( resample_filter->filter == PointFilter ) {
1249 resample_filter->do_interpolate = MagickTrue;
1250 return; /* EWA turned off - nothing more to do */
1253 resize_filter = AcquireResizeFilter(resample_filter->image,
1254 resample_filter->filter,MagickTrue,resample_filter->exception);
1255 if (resize_filter == (ResizeFilter *) NULL) {
1256 (void) ThrowMagickException(resample_filter->exception,GetMagickModule(),
1257 ModuleError, "UnableToSetFilteringValue",
1258 "Fall back to Interpolated 'Point' filter");
1259 resample_filter->filter = PointFilter;
1260 resample_filter->do_interpolate = MagickTrue;
1261 return; /* EWA turned off - nothing more to do */
1264 /* Get the practical working support for the filter,
1265 * after any API call blur factors have been accoded for.
1268 resample_filter->support = GetResizeFilterSupport(resize_filter);
1270 resample_filter->support = 2.0; /* fixed support size for HQ-EWA */
1274 /* Fill the LUT with the weights from the selected filter function */
1280 /* Scale radius so the filter LUT covers the full support range */
1281 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1282 for(Q=0; Q<WLUT_WIDTH; Q++)
1283 resample_filter->filter_lut[Q] = (double)
1284 GetResizeFilterWeight(resize_filter,sqrt((double)Q)*r_scale);
1286 /* finished with the resize filter */
1287 resize_filter = DestroyResizeFilter(resize_filter);
1290 /* save the filter and the scaled ellipse bounds needed for filter */
1291 resample_filter->filter_def = resize_filter;
1292 resample_filter->F = resample_filter->support*resample_filter->support;
1296 Adjust the scaling of the default unit circle
1297 This assumes that any real scaling changes will always
1298 take place AFTER the filter method has been initialized.
1300 ScaleResampleFilter(resample_filter, 1.0, 0.0, 0.0, 1.0);
1304 This is old code kept as a reference only. Basically it generates
1305 a Gaussian bell curve, with sigma = 0.5 if the support is 2.0
1307 Create Normal Gaussian 2D Filter Weighted Lookup Table.
1308 A normal EWA guassual lookup would use exp(Q*ALPHA)
1309 where Q = distance squared from 0.0 (center) to 1.0 (edge)
1310 and ALPHA = -4.0*ln(2.0) ==> -2.77258872223978123767
1311 The table is of length 1024, and equates to support radius of 2.0
1312 thus needs to be scaled by ALPHA*4/1024 and any blur factor squared
1314 The it comes from reference code provided by Fred Weinhaus.
1316 r_scale = -2.77258872223978123767/(WLUT_WIDTH*blur*blur);
1317 for(Q=0; Q<WLUT_WIDTH; Q++)
1318 resample_filter->filter_lut[Q] = exp((double)Q*r_scale);
1319 resample_filter->support = WLUT_WIDTH;
1323 #if defined(MAGICKCORE_OPENMP_SUPPORT)
1327 if (IfStringTrue(GetImageArtifact(resample_filter->image,
1328 "resample:verbose")) )
1335 /* Debug output of the filter weighting LUT
1336 Gnuplot the LUT data, the x scale index has been adjusted
1337 plot [0:2][-.2:1] "lut.dat" with lines
1338 The filter values should be normalized for comparision
1341 printf("# Resampling Filter LUT (%d values) for '%s' filter\n",
1342 WLUT_WIDTH, CommandOptionToMnemonic(MagickFilterOptions,
1343 resample_filter->filter) );
1345 printf("# Note: values in table are using a squared radius lookup.\n");
1346 printf("# As such its distribution is not uniform.\n");
1348 printf("# The X value is the support distance for the Y weight\n");
1349 printf("# so you can use gnuplot to plot this cylindrical filter\n");
1350 printf("# plot [0:2][-.2:1] \"lut.dat\" with lines\n");
1353 /* Scale radius so the filter LUT covers the full support range */
1354 r_scale = resample_filter->support*sqrt(1.0/(double)WLUT_WIDTH);
1355 for(Q=0; Q<WLUT_WIDTH; Q++)
1356 printf("%8.*g %.*g\n",
1357 GetMagickPrecision(),sqrt((double)Q)*r_scale,
1358 GetMagickPrecision(),resample_filter->filter_lut[Q] );
1359 printf("\n\n"); /* generate a 'break' in gnuplot if multiple outputs */
1361 /* Output the above once only for each image, and each setting
1362 (void) DeleteImageArtifact(resample_filter->image,"resample:verbose");
1365 #endif /* FILTER_LUT */
1370 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1374 % 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 %
1378 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1380 % SetResampleFilterInterpolateMethod() sets the resample filter interpolation
1383 % The format of the SetResampleFilterInterpolateMethod method is:
1385 % MagickBooleanType SetResampleFilterInterpolateMethod(
1386 % ResampleFilter *resample_filter,const InterpolateMethod method)
1388 % A description of each parameter follows:
1390 % o resample_filter: the resample filter.
1392 % o method: the interpolation method.
1395 MagickExport MagickBooleanType SetResampleFilterInterpolateMethod(
1396 ResampleFilter *resample_filter,const PixelInterpolateMethod method)
1398 assert(resample_filter != (ResampleFilter *) NULL);
1399 assert(resample_filter->signature == MagickSignature);
1400 assert(resample_filter->image != (Image *) NULL);
1401 if (resample_filter->debug != MagickFalse)
1402 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1403 resample_filter->image->filename);
1404 resample_filter->interpolate=method;
1409 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1413 % 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 %
1417 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
1419 % SetResampleFilterVirtualPixelMethod() changes the virtual pixel method
1420 % associated with the specified resample filter.
1422 % The format of the SetResampleFilterVirtualPixelMethod method is:
1424 % MagickBooleanType SetResampleFilterVirtualPixelMethod(
1425 % ResampleFilter *resample_filter,const VirtualPixelMethod method)
1427 % A description of each parameter follows:
1429 % o resample_filter: the resample filter.
1431 % o method: the virtual pixel method.
1434 MagickExport MagickBooleanType SetResampleFilterVirtualPixelMethod(
1435 ResampleFilter *resample_filter,const VirtualPixelMethod method)
1437 assert(resample_filter != (ResampleFilter *) NULL);
1438 assert(resample_filter->signature == MagickSignature);
1439 assert(resample_filter->image != (Image *) NULL);
1440 if (resample_filter->debug != MagickFalse)
1441 (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",
1442 resample_filter->image->filename);
1443 resample_filter->virtual_pixel=method;
1444 if (method != UndefinedVirtualPixelMethod)
1445 (void) SetCacheViewVirtualPixelMethod(resample_filter->view,method);