vrotate(1Vi)															      vrotate(1Vi)

NAME

       vrotate - rotate an image

SYNOPSIS

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

DESCRIPTION

       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.

COMMAND LINE OPTIONS

       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.

SEE ALSO

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

AUTHOR

       Daniel Ko <ko@cs.ubc.ca>

Vista Version 1.12						   24 April 1993						      vrotate(1Vi)