A PPM file contains the following:
the width in pixels,
the height in pixels,
the maximum colour component value,
The rows are ordered from top to bottom with the pixels in
each row ordered from left to right. Each pixel is
represented as three values for red, green, and blue.
All parts are separated by
whitespace and numbers are in
decimal
ASCIII representation. A zero pixel component means
that colour is absent. Characters from a "#" to the next
end-of-line are ignored and 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
A "RAWBITS" variant has magic number "P6", pixel values are
stored as plain binary bytes, instead of ASCII decimal and no
whitespace is allowed after a single whitespace character
after the maximum colour component value which must be less
than or equal to 255.
(1998-02-06)