Plain Text View of PPM.TXT

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     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, 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
          giftoppm(1), gouldtoppm(1), ilbmtoppm(1), imgtoppm(1),
          mtvtoppm(1), pcxtoppm(1), pgmtoppm(1), pi1toppm(1),
          picttoppm(1), pjtoppm(1), qrttoppm(1), rawtoppm(1),
          rgb3toppm(1), sldtoppm(1), spctoppm(1), sputoppm(1),
          tgatoppm(1), ximtoppm(1), xpmtoppm(1), yuvtoppm(1),
          ppmtoacad(1), ppmtogif(1), ppmtoicr(1), ppmtoilbm(1),
          ppmtopcx(1), ppmtopgm(1), ppmtopi1(1), ppmtopict(1),
          ppmtopj(1), ppmtopuzz(1), ppmtorgb3(1), ppmtosixel(1),
          ppmtotga(1), ppmtouil(1), ppmtoxpm(1), ppmtoyuv(1),
          ppmdither(1), ppmforge(1), ppmhist(1), ppmmake(1),
          ppmpat(1), ppmquant(1), ppmquantall(1), ppmrelief(1),
          pnm(5), pgm(5), pbm(5)

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



















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