rawtopgm(1) - phpMan

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



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 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.


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 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.


       -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 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 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 back-
              wards 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 AT fysik4.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(0)

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