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>