NAME

       rawtopgm - convert raw grayscale bytes into a portable graymap

SYNOPSIS

       rawtopgm  [-bpp  [1|2]]  [-littleendian] [-maxval N] [-headerskip N] [-rowskip N] [-tb|-topbottom] [width
       height] [imagefile]

DESCRIPTION

       Reads raw grayscale values as input.  Produces a PGM file as output.  The input file is just  a  sequence
       of pure binary numbers, either one or two bytes each, either bigendian or littleendian, representing gray
       values.  They may be arranged either top to bottom, left to right or bottom to top, left to right.  There
       may  be arbitrary header information at the start of the file (to which rawtopgm pays no attention at all
       other than the header's size).

       Arguments to rawtopgm tell how to interpret the pixels (a function that  is  served  by  a  header  in  a
       regular graphics format).

       The width and height parameters tell the dimensions of the image.  If you omit these parameters, rawtopgm
       assumes  it  is a quadratic image and bases the dimensions on the size of the input stream.  If this size
       is not a perfect square, rawtopgm fails.

       When you don't specify width and height, rawtopgm reads the entire input stream  into  storage  at  once,
       which may take a lot of storage.  Otherwise, rawtopgm ordinarily stores only one row at a time.

       If you don't specify imagefile, or specify -, the input is from Standard Input.

       The PGM output is to Standard Output.

OPTIONS

       -maxval N
              N  is the maxval for the gray values in the input, and is also the maxval of the PGM output image.
              The default is the maximum value that can be represented in the number  of  bytes  used  for  each
              sample (i.e. 255 or 65535).

       -bpp [1|2]
              tells  the  number  of bytes that represent each sample in the input.  If the value is 2, The most
              significant byte is first in the stream.

              The default is 1 byte per sample.

       -littleendian
              says that the bytes of each input sample are  ordered  with  the  least  significant  byte  first.
              Without  this option, rawtopgm assumes MSB first.  This obviously has no effect when there is only
              one byte per sample.

       -headerskip N
              rawtopgm skips over N bytes at the beginning of the stream and reads the image immediately  after.
              The default is 0.

              This  is  useful  when  the  input  is actually some graphics format that has a descriptive header
              followed by an ordinary raster, and you don't have a program that understands the  header  or  you
              want to ignore the header.

       -rowskip N
              If  there is padding at the ends of the rows, you can skip it with this option.  Note that rowskip
              need not be an integer.  Amazingly, I once had an image with 0.376 bytes of padding per row.  This
              turned out to be due to a file-transfer problem, but I was still able to read the image.

              Skipping a fractional byte per row means skipping one byte per multiple rows.

       -bt -bottomfirst
              By default, rawtopgm assumes the pixels in the input go top to bottom,  left  to  right.   If  you
              specify  -bt  or  -bottomfirst,  rawtopgm assumes the pixels go bottom to top, left to right.  The
              Molecular Dynamics and Leica confocal format, for example, use the latter arrangement.

              If you don't specify -bt when you should or vice versa, the resulting image is upside down,  which
              you can correct with pnmflip .

              This option causes rawtopgm to read the entire input stream into storage at once, which may take a
              lot of storage.  Ordinarly, rawtopgm stores only one row at a time.

              For  backwards  compatibility,  rawtopgm  also accepts -tb and -topbottom to mean exactly the same
              thing.  The reasons these are named backwards is  that  the  original  author  thought  of  it  as
              specifying  that  the  wrong  results of assuming the data is top to bottom should be corrected by
              flipping the result top for bottom.  Today, we think of it as simply specifying the format of  the
              input data so that there are no wrong results.

SEE ALSO

       pgm(5), rawtoppm(1), pnmflip(1)

AUTHORS

       Copyright (C) 1989 by Jef Poskanzer.
       Modified June 1993 by Oliver Trepte, oliver@fysik4.kth.se

                                                14 September 2000                                    rawtopgm(1)