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 deci-
         mal.

       - 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 set-
       ting 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 automat-
       ically fall back on the slower but more general plain for-
       mat.

SEE ALSO
       giftoppm(1),   gouldtoppm(1),  ilbmtoppm(1),  imgtoppm(1),
       mtvtoppm(1), pcxtoppm(1), pgmtoppm(1), pi1toppm(1),  pict-
       toppm(1),     pjtoppm(1),     qrttoppm(1),    rawtoppm(1),
       rgb3toppm(1),   sldtoppm(1),   spctoppm(1),   sputoppm(1),
       tgatoppm(1),  ximtoppm(1),  xpmtoppm(1), yuvtoppm(1), ppm-
       toacad(1), ppmtogif(1),  ppmtoicr(1),  ppmtoilbm(1),  ppm-
       topcx(1),  ppmtopgm(1),  ppmtopi1(1),  ppmtopict(1),  ppm-
       topj(1), ppmtopuzz(1), ppmtorgb3(1),  ppmtosixel(1),  ppm-
       totga(1),     ppmtouil(1),    ppmtoxpm(1),    ppmtoyuv(1),
       ppmdither(1), ppmforge(1),  ppmhist(1),  ppmmake(1),  ppm-
       pat(1), ppmquant(1), ppmquantall(1), ppmrelief(1), pnm(5),
       pgm(5), pbm(5)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.