PGM.TXT

PGM.TXT


Remove Frame


     pgm(5)              AMIGA (12 November 1991)               pgm(5)



     NAME
          pgm - portable graymap file format

     DESCRIPTION
          The portable graymap format is a lowest common denominator
          grayscale file format.  The definition is as follows:

          - A "magic number" for identifying the file type.  A pgm
            file's magic number is the two characters "P2".

          - Whitespace (blanks, TABs, CRs, LFs).

          - A width, formatted as ASCII characters in decimal.

          - Whitespace.

          - A height, again in ASCII decimal.

          - Whitespace.

          - The maximum gray value, again in ASCII decimal.

          - Whitespace.

          - Width * height gray values, each in ASCII decimal, between
            0 and the specified maximum value, separated by
            whitespace, starting at the top-left corner of the
            graymap, proceeding in normal English reading order.  A
            value of 0 means black, and the maximum value means white.

          - 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 graymap in this format:
          P2
          # feep.pgm
          24 7
          15
          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
          0  3  3  3  3  0  0  7  7  7  7  0  0 11 11 11 11  0  0 15 15 15 15  0
          0  3  0  0  0  0  0  7  0  0  0  0  0 11  0  0  0  0  0 15  0  0 15  0
          0  3  3  3  0  0  0  7  7  7  0  0  0 11 11 11  0  0  0 15 15 15 15  0
          0  3  0  0  0  0  0  7  0  0  0  0  0 11  0  0  0  0  0 15  0  0  0  0
          0  3  0  0  0  0  0  7  7  7  7  0  0 11 11 11 11  0  0 15  0  0  0  0
          0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  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
          graymap.




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     pgm(5)              AMIGA (12 November 1991)               pgm(5)



          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 "P5" instead of "P2".

          - The gray values are stored as plain bytes, instead of
            ASCII decimal.

          - No whitespace is allowed in the grays section, 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 pgm 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
          fitstopgm(1), fstopgm(1), hipstopgm(1), lispmtopgm(1),
          psidtopgm(1), rawtopgm(1), pgmbentley(1), pgmcrater(1),
          pgmedge(1), pgmenhance(1), pgmhist(1), pgmnorm(1),
          pgmoil(1), pgmramp(1), pgmtexture(1), pgmtofits(1),
          pgmtofs(1), pgmtolispm(1), pgmtopbm(1), pnm(5), pbm(5),
          ppm(5)

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
























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