.TH ppmrotate 1 "15 February 1989"
.SH NAME
ppmrotate - rotate a portable pixmap by some angle
.SH SYNOPSIS
ppmrotate angle [ppmfile]
.SH DESCRIPTION
Reads a portable pixmap as input.
Rotates it by the specified angle and produces a portable
pixmap as output.
The angle is in degrees (floating point), measured counter-clockwise.
It can be negative, but it should be between -90 and 90.
.PP
The rotation algorithm is Alan Paeth's three-shear method.
Each shear is implemented by looping over the source pixels and distributing
fractions to each of the destination pixels.
.SH REFERENCES
"A Fast Algorithm for General Raster Rotation" by Alan Paeth,
Graphics Interface '86, pp. 77-81.
.SH "SEE ALSO"
ppmshear(1), pnmflip(1), ppm(5)
.SH AUTHOR
Copyright (C) 1989 by Jef Poskanzer.

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation.  This software is provided "as is" without express or
implied warranty.