ppm

NAME

DESCRIPTION

-

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, proceeding 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 possible, accepting anything that looks remotely like a pixmap.

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:

-

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, and only a single character of whitespace (typically a newline) is allowed after the maxval.

-

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 plain format.  

SEE ALSO

AUTHOR

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AUTHOR