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rawtopgm(1)									      rawtopgm(1)

       rawtopgm - convert raw grayscale bytes into a portable graymap

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

       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

       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 stor-
       age  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.

       -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 num-
	      ber 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.

	      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  descrip-
	      tive  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 prob-
	      lem, 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 exam-
	      ple, 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

	      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.

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

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

					14 September 2000			      rawtopgm(1)
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