% %
% %
% %
-% C a n n y E d g e I m a g e %
-% %
-% %
-% %
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-%
-% CannyEdgeImage() uses a multi-stage algorithm to detect a wide range of
-% edges in images.
-%
-% The format of the EdgeImage method is:
-%
-% Image *CannyEdgeImage(const Image *image,const double radius,
-% const double sigma,const double low_percent,const double high_percent,
-% const size_t threshold,ExceptionInfo *exception)
-%
-% A description of each parameter follows:
-%
-% o image: the image.
-%
-% o channel: the channel type.
-%
-% o radius: the radius of the gaussian smoothing filter.
-%
-% o sigma: the sigma of the gaussian smoothing filter.
-%
-% o low_percent: percentage of pixels in the low threshold.
-%
-% o high_percent: percentage of pixels in the high threshold.
-%
-% o exception: return any errors or warnings in this structure.
-%
-*/
-
-typedef struct _CannyInfo
-{
- double
- magnitude,
- intensity;
-
- int
- orientation;
-} CannyInfo;
-
-static MagickBooleanType IsAuthenticPixel(const Image *image,const ssize_t x,
- const ssize_t y)
-{
- if ((x < 0) || (x >= (ssize_t) image->columns))
- return(MagickFalse);
- if ((y < 0) || (y >= (ssize_t) image->rows))
- return(MagickFalse);
- return(MagickTrue);
-}
-
-static MagickBooleanType TraceEdge(Image *edge_image,CacheView *edge_view,
- MatrixInfo *pixel_cache,const ssize_t x,const ssize_t y,
- const double threshold,ExceptionInfo *exception)
-{
- CannyInfo
- pixel;
-
- Quantum
- *q;
-
- MagickBooleanType
- status;
-
- q=GetCacheViewAuthenticPixels(edge_view,x,y,1,1,exception);
- if ((q != (Quantum *) NULL) && (GetPixelIntensity(edge_image,q) == 0))
- {
- ssize_t
- v;
-
- *q=QuantumRange;
- status=SyncCacheViewAuthenticPixels(edge_view,exception);
- if (status != MagickFalse)
- {
- for (v=(-1); v <= 1; v++)
- {
- ssize_t
- u;
-
- for (u=(-1); u <= 1; u++)
- {
- if (((y != 0) || (u != 0)) &&
- (IsAuthenticPixel(edge_image,x+u,y+v) != MagickFalse))
- {
- (void) GetMatrixElement(pixel_cache,x+u,y+v,&pixel);
- if (pixel.intensity >= threshold)
- {
- status=TraceEdge(edge_image,edge_view,pixel_cache,x+u,y+v,
- threshold,exception);
- if (status != MagickFalse)
- return(MagickTrue);
- }
- }
- }
- }
- return(MagickTrue);
- }
- }
- return(MagickFalse);
-}
-
-MagickExport Image *CannyEdgeImage(const Image *image,const double radius,
- const double sigma,const double low_percent,const double high_percent,
- ExceptionInfo *exception)
-{
- CacheView
- *edge_view;
-
- char
- geometry[MaxTextExtent];
-
- double
- high_threshold,
- low_threshold;
-
- Image
- *edge_image;
-
- KernelInfo
- *kernel_info;
-
- MagickBooleanType
- status;
-
- MatrixInfo
- *pixel_cache;
-
- register ssize_t
- i;
-
- size_t
- *histogram,
- number_pixels;
-
- ssize_t
- count,
- y;
-
- assert(image != (const Image *) NULL);
- assert(image->signature == MagickSignature);
- if (image->debug != MagickFalse)
- (void) LogMagickEvent(TraceEvent,GetMagickModule(),"%s",image->filename);
- assert(exception != (ExceptionInfo *) NULL);
- assert(exception->signature == MagickSignature);
- /*
- Filter out noise before trying to locate and detect any edges.
- */
- (void) FormatLocaleString(geometry,MaxTextExtent,
- "blur:%.20gx%.20g;blur:%.20gx%.20g+90",radius,sigma,radius,sigma);
- kernel_info=AcquireKernelInfo(geometry);
- if (kernel_info == (KernelInfo *) NULL)
- ThrowImageException(ResourceLimitError,"MemoryAllocationFailed");
- edge_image=MorphologyApply(image,ConvolveMorphology,1,kernel_info,
- UndefinedCompositeOp,0.0,exception);
- kernel_info=DestroyKernelInfo(kernel_info);
- if (edge_image == (Image *) NULL)
- return((Image *) NULL);
- if (SetImageColorspace(edge_image,GRAYColorspace,exception) == MagickFalse)
- {
- edge_image=DestroyImage(edge_image);
- return((Image *) NULL);
- }
- /*
- Find the edge strength by taking the gradient of the image.
- */
- pixel_cache=AcquireMatrixInfo(edge_image->columns,edge_image->rows,
- sizeof(CannyInfo),exception);
- if (pixel_cache == (MatrixInfo *) NULL)
- {
- edge_image=DestroyImage(edge_image);
- return((Image *) NULL);
- }
- status=MagickTrue;
- edge_view=AcquireVirtualCacheView(edge_image,exception);
-#if defined(MAGICKCORE_OPENMP_SUPPORT)
- #pragma omp parallel for schedule(static,4) shared(status) \
- magick_threads(edge_image,edge_image,edge_image->rows,1)
-#endif
- for (y=0; y < (ssize_t) edge_image->rows; y++)
- {
- register const Quantum
- *restrict p;
-
- register ssize_t
- x;
-
- if (status == MagickFalse)
- continue;
- p=GetCacheViewVirtualPixels(edge_view,-1,y-1,edge_image->columns+2,3,
- exception);
- if (p == (const Quantum *) NULL)
- {
- status=MagickFalse;
- continue;
- }
- for (x=0; x < (ssize_t) edge_image->columns; x++)
- {
- CannyInfo
- pixel;
-
- double
- dx,
- dy;
-
- register const Quantum
- *restrict kernel_pixels;
-
- ssize_t
- v;
-
- static double
- Gx[3][3] =
- {
- { -1.0, 0.0, +1.0 },
- { -2.0, 0.0, +2.0 },
- { -1.0, 0.0, +1.0 }
- },
- Gy[3][3] =
- {
- { +1.0, +2.0, +1.0 },
- { 0.0, 0.0, 0.0 },
- { -1.0, -2.0, -1.0 }
- };
-
- (void) ResetMagickMemory(&pixel,0,sizeof(pixel));
- dx=0.0;
- dy=0.0;
- kernel_pixels=p;
- for (v=0; v < 3; v++)
- {
- ssize_t
- u;
-
- for (u=0; u < 3; u++)
- {
- double
- intensity;
-
- intensity=GetPixelIntensity(edge_image,kernel_pixels+u);
- dx+=Gx[v][u]*intensity;
- dy+=Gy[v][u]*intensity;
- }
- kernel_pixels+=edge_image->columns+2;
- }
- pixel.magnitude=sqrt(dx*dx+dy*dy);
- pixel.orientation=2;
- if (dx != 0.0)
- {
- double
- theta;
-
- theta=dy/dx;
- if (theta < 0.0)
- {
- if (theta < -2.41421356237)
- pixel.orientation=0;
- else
- if (theta < -0.414213562373)
- pixel.orientation=1;
- else
- pixel.orientation=2;
- }
- else
- {
- if (theta > 2.41421356237)
- pixel.orientation=0;
- else
- if (theta > 0.414213562373)
- pixel.orientation=3;
- else
- pixel.orientation=2;
- }
- }
- if (SetMatrixElement(pixel_cache,x,y,&pixel) == MagickFalse)
- continue;
- p+=GetPixelChannels(edge_image);
- }
- }
- edge_view=DestroyCacheView(edge_view);
- /*
- Non-maxima suppression; reset edge image.
- */
- histogram=(size_t *) AcquireQuantumMemory(65536,sizeof(*histogram));
- if (histogram == (size_t *) NULL)
- {
- pixel_cache=DestroyMatrixInfo(pixel_cache);
- edge_image=DestroyImage(edge_image);
- return((Image *) NULL);
- }
- (void) ResetMagickMemory(histogram,0,65536*sizeof(*histogram));
- edge_view=AcquireAuthenticCacheView(edge_image,exception);
-#if defined(MAGICKCORE_OPENMP_SUPPORT)
- #pragma omp parallel for schedule(static,4) shared(status) \
- magick_threads(edge_image,edge_image,edge_image->rows,1)
-#endif
- for (y=0; y < (ssize_t) edge_image->rows; y++)
- {
- register Quantum
- *restrict q;
-
- register ssize_t
- x;
-
- if (status == MagickFalse)
- continue;
- q=GetCacheViewAuthenticPixels(edge_view,0,y,edge_image->columns,1,
- exception);
- if (q == (Quantum *) NULL)
- {
- status=MagickFalse;
- continue;
- }
- for (x=0; x < (ssize_t) edge_image->columns; x++)
- {
- CannyInfo
- alpha_pixel,
- beta_pixel,
- pixel;
-
- (void) GetMatrixElement(pixel_cache,x,y,&pixel);
- switch (pixel.orientation)
- {
- case 0:
- {
- /*
- 0 degrees.
- */
- (void) GetMatrixElement(pixel_cache,x,y-1,&alpha_pixel);
- (void) GetMatrixElement(pixel_cache,x,y+1,&beta_pixel);
- break;
- }
- case 1:
- {
- /*
- 45 degrees.
- */
- (void) GetMatrixElement(pixel_cache,x-1,y-1,&alpha_pixel);
- (void) GetMatrixElement(pixel_cache,x+1,y+1,&beta_pixel);
- break;
- }
- case 2:
- {
- /*
- 90 degrees.
- */
- (void) GetMatrixElement(pixel_cache,x-1,y,&alpha_pixel);
- (void) GetMatrixElement(pixel_cache,x+1,y,&beta_pixel);
- }
- case 3:
- {
- /*
- 135 degrees.
- */
- (void) GetMatrixElement(pixel_cache,x+1,y-1,&alpha_pixel);
- (void) GetMatrixElement(pixel_cache,x-1,y+1,&beta_pixel);
- }
- }
- pixel.intensity=pixel.magnitude;
- if ((pixel.magnitude < alpha_pixel.magnitude) ||
- (pixel.magnitude < beta_pixel.magnitude))
- pixel.intensity=0;
- else
- if (pixel.magnitude > QuantumRange)
- pixel.intensity=QuantumRange;
- (void) SetMatrixElement(pixel_cache,x,y,&pixel);
-#if defined(MAGICKCORE_OPENMP_SUPPORT)
- #pragma omp critical (MagickCore_CannyEdgeImage)
-#endif
- histogram[ScaleQuantumToShort(ClampToQuantum(pixel.intensity))]++;
- *q=0;
- q+=GetPixelChannels(edge_image);
- }
- if (SyncCacheViewAuthenticPixels(edge_view,exception) == MagickFalse)
- status=MagickFalse;
- }
- edge_view=DestroyCacheView(edge_view);
- /*
- Estimate hysteresis threshold.
- */
- number_pixels=(size_t) (low_percent*(image->columns*image->rows-
- histogram[0]));
- count=0;
- for (i=65535; count < (ssize_t) number_pixels; i--)
- count+=histogram[i];
- high_threshold=(double) ScaleShortToQuantum((unsigned short) i);
- for (i=0; histogram[i] == 0; i++) ;
- low_threshold=high_percent*(high_threshold+
- ScaleShortToQuantum((unsigned short) i));
- histogram=(size_t *) RelinquishMagickMemory(histogram);
- /*
- Hysteresis thresholding.
- */
- edge_view=AcquireAuthenticCacheView(edge_image,exception);
-#if defined(MAGICKCORE_OPENMP_SUPPORT)
- #pragma omp parallel for schedule(static,4) shared(status) \
- magick_threads(edge_image,edge_image,edge_image->rows,1)
-#endif
- for (y=0; y < (ssize_t) edge_image->rows; y++)
- {
- register Quantum
- *restrict q;
-
- register ssize_t
- x;
-
- if (status == MagickFalse)
- continue;
- q=GetCacheViewAuthenticPixels(edge_view,0,y,edge_image->columns,1,
- exception);
- if (q == (Quantum *) NULL)
- {
- status=MagickFalse;
- continue;
- }
- for (x=0; x < (ssize_t) edge_image->columns; x++)
- {
- CannyInfo
- pixel;
-
- (void) GetMatrixElement(pixel_cache,x,y,&pixel);
- if (pixel.intensity >= high_threshold)
- (void) TraceEdge(edge_image,edge_view,pixel_cache,x,y,low_threshold,
- exception);
- }
- if (SyncCacheViewAuthenticPixels(edge_view,exception) == MagickFalse)
- status=MagickFalse;
- }
- edge_view=DestroyCacheView(edge_view);
- pixel_cache=DestroyMatrixInfo(pixel_cache);
- return(edge_image);
-}
-\f
-/*
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% %
-% %
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% C o n v o l v e I m a g e %
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% %
projects / imagemagick / blobdiff