% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
-% The XShearImage, and YShearImage methods are based on the paper "A Fast
+% The XShearImage() and YShearImage() methods are based on the paper "A Fast
% Algorithm for General Raster Rotatation" by Alan W. Paeth, Graphics
-% Interface '86 (Vancouver). RotateImage is adapted from a similar method
-% based on the Paeth paper written by Michael Halle of the Spatial Imaging
-% Group, MIT Media Lab.
+% Interface '86 (Vancouver). ShearRotateImage() is adapted from a similar
+% method based on the Paeth paper written by Michael Halle of the Spatial
+% Imaging Group, MIT Media Lab.
%
*/
\f
shear_image->page.height=0;
return(shear_image);
}
+\f
+/*
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% %
+% %
+% %
+% S h e a r R o t a t e I m a g e %
+% %
+% %
+% %
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% ShearRotateImage() creates a new image that is a rotated copy of an existing
+% one. Positive angles rotate counter-clockwise (right-hand rule), while
+% negative angles rotate clockwise. Rotated images are usually larger than
+% the originals and have 'empty' triangular corners. X axis. Empty
+% triangles left over from shearing the image are filled with the background
+% color defined by member 'background_color' of the image. ShearRotateImage
+% allocates the memory necessary for the new Image structure and returns a
+% pointer to the new image.
+%
+% ShearRotateImage() is based on the paper "A Fast Algorithm for General
+% Raster Rotatation" by Alan W. Paeth. ShearRotateImage is adapted from a
+% similar method based on the Paeth paper written by Michael Halle of the
+% Spatial Imaging Group, MIT Media Lab.
+%
+% The format of the ShearRotateImage method is:
+%
+% Image *ShearRotateImage(const Image *image,const double degrees,
+% ExceptionInfo *exception)
+%
+% A description of each parameter follows.
+%
+% o image: the image.
+%
+% o degrees: Specifies the number of degrees to rotate the image.
+%
+% o exception: return any errors or warnings in this structure.
+%
+*/
+MagickExport Image *ShearRotateImage(const Image *image,const double degrees,
+ ExceptionInfo *exception)
+{
+ Image
+ *integral_image,
+ *rotate_image;
+
+ MagickBooleanType
+ status;
+
+ MagickRealType
+ angle;
+
+ PointInfo
+ shear;
+
+ RectangleInfo
+ border_info;
+
+ size_t
+ height,
+ rotations,
+ width,
+ y_width;
+
+ ssize_t
+ x_offset,
+ y_offset;
+
+ /*
+ Adjust rotation angle.
+ */
+ assert(image != (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);
+ angle=degrees;
+ while (angle < -45.0)
+ angle+=360.0;
+ for (rotations=0; angle > 45.0; rotations++)
+ angle-=90.0;
+ rotations%=4;
+ /*
+ Calculate shear equations.
+ */
+ integral_image=IntegralRotateImage(image,rotations,exception);
+ if (integral_image == (Image *) NULL)
+ ThrowImageException(ResourceLimitError,"MemoryAllocationFailed");
+ shear.x=(-tan((double) DegreesToRadians(angle)/2.0));
+ shear.y=sin((double) DegreesToRadians(angle));
+ if ((shear.x == 0.0) && (shear.y == 0.0))
+ return(integral_image);
+ if (SetImageStorageClass(integral_image,DirectClass,exception) == MagickFalse)
+ {
+ integral_image=DestroyImage(integral_image);
+ return(integral_image);
+ }
+ if (integral_image->matte == MagickFalse)
+ (void) SetImageAlphaChannel(integral_image,OpaqueAlphaChannel,exception);
+ /*
+ Compute image size.
+ */
+ width=image->columns;
+ height=image->rows;
+ if ((rotations == 1) || (rotations == 3))
+ {
+ width=image->rows;
+ height=image->columns;
+ }
+ y_width=width+(ssize_t) floor(fabs(shear.x)*height+0.5);
+ x_offset=(ssize_t) ceil((double) width+((fabs(shear.y)*height)-width)/2.0-
+ 0.5);
+ y_offset=(ssize_t) ceil((double) height+((fabs(shear.y)*y_width)-height)/2.0-
+ 0.5);
+ /*
+ Surround image with a border.
+ */
+ integral_image->border_color=integral_image->background_color;
+ integral_image->compose=CopyCompositeOp;
+ border_info.width=(size_t) x_offset;
+ border_info.height=(size_t) y_offset;
+ rotate_image=BorderImage(integral_image,&border_info,image->compose,
+ exception);
+ integral_image=DestroyImage(integral_image);
+ if (rotate_image == (Image *) NULL)
+ ThrowImageException(ResourceLimitError,"MemoryAllocationFailed");
+ /*
+ Rotate the image.
+ */
+ status=XShearImage(rotate_image,shear.x,width,height,x_offset,(ssize_t)
+ (rotate_image->rows-height)/2,exception);
+ if (status == MagickFalse)
+ {
+ rotate_image=DestroyImage(rotate_image);
+ return((Image *) NULL);
+ }
+ status=YShearImage(rotate_image,shear.y,y_width,height,(ssize_t)
+ (rotate_image->columns-y_width)/2,y_offset,exception);
+ if (status == MagickFalse)
+ {
+ rotate_image=DestroyImage(rotate_image);
+ return((Image *) NULL);
+ }
+ status=XShearImage(rotate_image,shear.x,y_width,rotate_image->rows,(ssize_t)
+ (rotate_image->columns-y_width)/2,0,exception);
+ if (status == MagickFalse)
+ {
+ rotate_image=DestroyImage(rotate_image);
+ return((Image *) NULL);
+ }
+ status=CropToFitImage(&rotate_image,shear.x,shear.y,(MagickRealType) width,
+ (MagickRealType) height,MagickTrue,exception);
+ if (status == MagickFalse)
+ {
+ rotate_image=DestroyImage(rotate_image);
+ return((Image *) NULL);
+ }
+ rotate_image->compose=image->compose;
+ rotate_image->page.width=0;
+ rotate_image->page.height=0;
+ return(rotate_image);
+}
projects / imagemagick / commitdiff