NAME
    rawtopgm - convert raw grayscale bytes into a portable graymap

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

DESCRIPTION
    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 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 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  Stan-
    dard 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 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, raw-
    topgm 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 pnm-
    flip .

    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 -top-
    bottom 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 bot-
    tom.  Today, we think of it as simply specifying the format of
    the input data so that there are no wrong results.

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

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