.TH pnmquadrilateral 1 "21 April 2009"
.IX pnmquadrilateral
.SH NAME
pnmquadrilateral - quadrilateral transformation of a portable anymap
.SH SYNOPSIS
.B pnmquadrilateral
.RB [ -supersamplesize
.IR n ]
.I x1 y1 x2 y2 x3 y3 x4 y4
.RI [ pnmfile ]
.SH DESCRIPTION
Reads a portable anymap as input.
Scales it to fit the specified four corner coordinates,
and produces a portable anymap as output.
If the input image is in color, the output will be too,
otherwise it will be grayscale.
The output image will be the same dimensions as the input, with
the unused pixels set to black.
.PP
The first x,y pair specifies where the upper left corner of
the input image should go.
The second x,y pair is where the upper right corner goes.
Third pair, lower left; fourth pair, lower right.
.PP
The -supersamplesize flag lets you improve either the quality or the
speed of the transformation.
Its default value is 3, which means each pixel of the input image
gets supersampled in a 3 x 3 grid, which takes nine times longer
but gives better-looking results.
If you raise the value above 3 you can get even smoother results,
at the cost of even more time; conversely, if you lower the
value to 2 or even 1, the program will run faster but the output
image will look blocky.
.SH "SEE ALSO"
pnmscale(1), pbmplus(1)
.SH AUTHOR
Copyright (C) 1989, 2009 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.