rawtopgm

   Updated: 14 September 2000
   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.

   rawtopgm reads raw grayscale values as input	 and  produces	a
PGM image as
   output.  The input file is just a sequence of pure binary num-
bers, either one
   or two bytes each, either bigendian	or  littleendian,  repre-
senting 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	 informa-
tion 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 im-
age. If you
   omit these parameters, rawtopgm assumes it is a quadratic  im-
age 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 max-
imum 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 -bottom-
first, 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 pam-
flip.
	  This option causes rawtopgm to read  the  entire  input
stream into
	  storage at once, which may take a lot of storage. Ordi-
narly, 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, rawtoppm, pamflip

AUTHORS

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



Table Of Contents

     * NAME
     * SYNOPSIS
     * DESCRIPTION
     * OPTIONS
     * SEE ALSO
     * AUTHORS

UNIX/Linux commands referenced on this page:

1. convert
2. raw
3. as
4. file
5. top
6. at
7. which
8. size
9. rawtoppm