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       vrotate - rotate an image


       vrotate [-angle angle] [- option ...] [infile] [outfile]


       vrotate  rotates  each  input  image  by  the  specified angle, producing a file of output
       images. The rotation is done by first rotating the image  by  a  multiple  of  90  degrees
       (using  flips  and transpositions) to an angle nearest to the specified angle, and then by
       completing the rotation using Alan Paeth's three-shear method.

       Because each pixel in the rotated image is a weighted average of the corresponding  pixels
       in  the original image, the set of colors (or gray shades) used by the original image will
       not be preserved in the rotated image.

       In general, the edges of the rotated image will  not  be  parallel  to  the  vertical  and
       horizontal  axes.  In such cases, the output image will be the smallest rectangular region
       containing the whole rotated image. Portions of  the  output  image  not  covered  by  the
       rotated image will be filled with zeros.


       vrotate accepts the following options in any order:

       -help          Prints a message describing options.

       -in infile     Specifies a Vista data file containing the input images.

       -out outfile   Specifies where to write the output images as a Vista data file.

       -angle angle   Specifies  the  angle  of  rotation  in  degrees.  Positive  values  rotate
                      counterclockwise; negative ones rotate clockwise. Default: 90.

       Input and output files can be specified on the command line or allowed to default  to  the
       standard input and output streams.


       VImage(3Vi), Vista(7Vi)
       ``A  Fast  Algorithm  for General Raster Rotation'' by Alan Paeth, Graphics Interface '86,
       pp. 77-81.


       Daniel Ko <>