Manual: rawtopgm

Rawtopgm User Manual(1)				   General Commands Manual			     Rawtopgm User Manual(1)

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	 op‐
	      tion, 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 cor‐
	      rect 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 cor‐
	      rected  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)