Rawtopgm User Manual(0)                 Rawtopgm User Manual(0)



Table Of Contents

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 pro-
       duces 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
       -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 rep-
              resented 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.   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(1), rawtoppm(1), pamflip(1)


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



netpbm documentation   14 September 2000Rawtopgm User Manual(0)
