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pnmrotate
!!!pnmrotate
NAME
SYNOPSIS
DESCRIPTION
REFERENCES
SEE ALSO
AUTHOR
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!!NAME


pnmrotate - rotate a portable anymap by some angle
!!SYNOPSIS


__pnmrotate__ [[__-noantialias__] ''angle''
[[''pnmfile'']
!!DESCRIPTION


Reads a portable anymap as input. Rotates it by the
specified angle and produces a portable anymap as output. If
the input file is in color, the output will be too,
otherwise it will be grayscale. The angle is in degrees
(floating point), measured counter-clockwise. It can be
negative, but it should be between -90 and 90. Also, for
rotations greater than 45 degrees you may get better results
if you first use ''pnmflip'' to do a 90 degree rotation
and then ''pnmrotate'' less than 45 degrees back the
other direction


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. This has an
-noantialias__ flag. This does
the shearing by moving pixels without changing their values.
If you want anti-aliasing and don't care about the precise
colors, but still need a limited *number* of colors, you can
run the result through ''ppmquant''.


All flags can be abbreviated to their shortest unique
prefix.
!!REFERENCES


!!SEE ALSO


pnmshear(1), pnmflip(1), pnm(5), ppmquant(1)
!!AUTHOR


Copyright (C) 1989, 1991 by Jef Poskanzer.
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Last edited on Monday, June 3, 2002 6:50:57 pm by "perry"

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