.TH ppm 5 "05 September 1989"
.SH NAME
ppm - portable pixmap file format
.SH DESCRIPTION
The portable pixmap format is a lowest common denominator color image
file format.
The definition is as follows:
.IP - 2
A "magic number" for identifying the file type.
A ppm file's magic number is the two characters "P3".
.IP - 2
Whitespace (blanks, TABs, CRs, LFs).
.IP - 2
A width, formatted as ASCII characters in decimal.
.IP - 2
Whitespace.
.IP - 2
A height, again in ASCII decimal.
.IP - 2
Whitespace.
.IP - 2
The maximum color-component value, again in ASCII decimal.
.IP - 2
Whitespace.
.IP - 2
Width * height pixels, each three ASCII decimal values between 0 and the
specified maximum value, starting at the top-left
corner of the pixmap, proceding in normal English reading order.
The three values for each pixel represent red, green, and blue, respectively;
a value of 0 means that color is off, and the maximum value means that color
is maxxed out.
.IP - 2
Characters from a "#" to the next end-of-line are ignored (comments).
.IP - 2
No line should be longer than 70 characters.
.PP
Here is an example of a small pixmap in this format:
.PP
.nf
P3
# feep.ppm
4 4
15
 0  0  0    0  0  0    0  0  0   15  0 15
 0  0  0    0 15  7    0  0  0    0  0  0
 0  0  0    0  0  0    0 15  7    0  0  0
15  0 15    0  0  0    0  0  0    0  0  0
.fi
.PP
Programs that read this format should be as lenient as possible,
accepting anything that looks remotely like a pixmap.
.PP
There is also a variant on the format, available
by setting the RAWBITS option at compile time.  This variant is
different in the following ways:
.IP - 2
The "magic number" is "P6" instead of "P3".
.IP - 2
The pixel values are stored as plain bytes, instead of ASCII decimal.
.IP - 2
Whitespace is not allowed in the pixels area.
.IP - 2
The files are smaller and many times faster to read and write.
.PP
Note that this raw format can only be used for maxvals less than
or equal to 255.
If you use the PPM library and try to write a file with a larger maxval,
it will automatically fall back on the slower but more general ASCII
format.
.SH "SEE ALSO"
giftoppm(1), ilbmtoppm(1), imgtoppm(1), mtvtoppm(1), qrttoppm(1), rasttoppm(1),
tgatoppm(1), xwdtoppm(1),
ppmtogif(1), ppmtoilbm(1), ppmtopgm(1), ppmtops(1), ppmtorast(1), ppmtoxwd(1),
ppmarith(1), ppmconvol(1), ppmcscale(1), ppmhist(1), ppmquant(1), ppmrotate(1),
ppmscale(1), ppmshear(1),
pnm(5), pgm(5), pbm(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.