NAME

       rawtopgm - convert raw grayscale bytes to a PGM image

SYNOPSIS

       rawtopgm

       [-bpp [1|2]]

       [-littleendian]

       [-maxval N]

       [-headerskip N]

       [-rowskip N]

       [-tb|-topbottom]

       [width height]

       [imagefile]

DESCRIPTION

       This program is part of Netpbm(1).

       rawtopgm  reads raw grayscale values as input and produces a PGM image 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

       In addition to the options common to all programs based on libnetpbm (most notably  -quiet,  see   Common
       Options ), rawtopgm recognizes the following command line 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 pamflip.

              This option causes rawtopgm to read the entire input stream into storage at once, which may take a
              lot of storage.  Normally, 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(1), rawtoppm(1), pamflip(1)

AUTHORS

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

DOCUMENT SOURCE

       This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The  master  documentation
       is at

              http://netpbm.sourceforge.net/doc/rawtopgm.html

netpbm documentation                            14 September 2000                        Rawtopgm User Manual(1)