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ppm(5) PBM Plus ppm(5)
NAME
ppm - portable pixmap file format
DESCRIPTION
The portable pixmap format is a lowest common denominator
color image file format. The definition is as follows:
- A "magic number" for identifying the file type. A ppm
file's magic number is the two characters "P3".
- Whitespace (blanks, TABs, CRs, LFs).
- A width, formatted as ASCII characters in decimal.
- Whitespace.
- A height, again in ASCII decimal.
- Whitespace.
- The maximum color-component value, again in ASCII decimal.
- Whitespace.
- 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.
- Characters from a "#" to the next end-of-line are ignored
(comments).
- No line should be longer than 70 characters.
Here is an example of a small pixmap in this format:
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
Programs that read this format should be as lenient as pos-
sible, accepting anything that looks remotely like a pixmap.
Printed 5/25/90 05 September 1989 1
ppm(5) PBM Plus ppm(5)
There is also a variant on the format, available by setting
the RAWBITS option at compile time. This variant is dif-
ferent in the following ways:
- The "magic number" is "P6" instead of "P3".
- The pixel values are stored as plain bytes, instead of
ASCII decimal.
- Whitespace is not allowed in the pixels area.
- The files are smaller and many times faster to read and
write.
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.
SEE ALSO
giftoppm(1), ilbmtoppm(1), imgtoppm(1), mtvtoppm(1),
qrttoppm(1), rasttoppm(1), tgatoppm(1), xwdtoppm(1), ppmto-
gif(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)
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 docu-
mentation. This software is provided "as is" without
express or implied warranty.
Printed 5/25/90 05 September 1989 2