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)
