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Rawtopgm User Manual
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rawtopgm
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Updated: 14 September 2000
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Table Of Contents
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NAME
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rawtopgm - convert raw grayscale bytes to a PGM image
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SYNOPSIS
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\fBrawtopgm\fR
[\fB-bpp\fR [\fB1\fR|\fB2\fR]]
[\fB-littleendian\fR]
[\fB-maxval\fR \fIN\fR]
[\fB-headerskip\fR \fIN\fR]
[\fB-rowskip\fR \fIN\fR]
[\fB-tb\fR|\fB-topbottom\fR]
[\fIwidth\fR \fIheight\fR]
[\fIimagefile\fR]
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DESCRIPTION
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This program is part of Netpbm.
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\fBrawtopgm\fR 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
\fBrawtopgm\fR pays no attention at all other than the header's
size).
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Arguments to \fBrawtopgm\fR tell how to interpret the pixels (a
function that is served by a header in a regular graphics format).
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The \fIwidth\fR and \fIheight\fR parameters tell the dimensions
of the image.  If you omit these parameters, \fBrawtopgm\fR 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, \fBrawtopgm\fR
fails.
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When you don't specify \fIwidth\fR and \fIheight\fR,
\fBrawtopgm\fR reads the entire input stream into storage at once,
which may take a lot of storage.  Otherwise, \fBrawtopgm\fR
ordinarily stores only one row at a time.
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If you don't specify \fIimagefile\fR, or specify \fB-\fR, the
input is from Standard Input.
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The PGM output is to Standard Output.
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OPTIONS
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.RS
.IP "\fB-maxval\fR \fIN\fR"
\fIN\fR 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).
.IP "\fB-bpp\fR [\fB1\fR|\fB2\fR]"
tells the number of bytes that represent each sample in the input.
If the value is \fB2\fR, The most significant byte is first in the
stream.
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The default is 1 byte per sample.
.IP "\fB-littleendian\fR"
says that the bytes of each input sample are ordered with the
least significant byte first.  Without this option, \fBrawtopgm\fR
assumes MSB first.  This obviously has no effect when there is only
one byte per sample.
.IP "\fB-headerskip\fR \fIN\fR"
\fBrawtopgm\fR skips over \fIN\fR bytes at the beginning of the
stream and reads the image immediately after.  The default is 0.
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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.
.IP "\fB-rowskip\fR \fIN\fR"
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.
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Skipping a fractional byte per row means skipping one byte per
multiple rows.
.IP "\fB-bt -bottomfirst\fR"
By default, \fBrawtopgm\fR assumes the pixels in the input go top
to bottom, left to right.  If you specify \fB-bt\fR or
\fB-bottomfirst\fR, \fBrawtopgm\fR assumes the pixels go bottom to
top, left to right.  The Molecular Dynamics and Leica confocal format,
for example, use the latter arrangement.
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If you don't specify \fB-bt\fR when you should or vice versa, the
resulting image is upside down, which you can correct with
\fBpamflip\fR.
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This option causes \fBrawtopgm\fR to read the entire input stream
into storage at once, which may take a lot of storage.  Ordinarly,
\fBrawtopgm\fR stores only one row at a time.
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For backwards compatibility, \fBrawtopgm\fR also accepts \fB-tb
\fR and \fB-topbottom\fR 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.
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SEE ALSO
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\fBpgm\fR,
\fBrawtoppm\fR,
\fBpamflip\fR
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AUTHORS
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Copyright (C) 1989 by Jef Poskanzer.
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Modified June 1993 by Oliver Trepte, oliver@fysik4.kth.se
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\l'5i'
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Table Of Contents
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.IP \(bu
NAME
.IP \(bu
SYNOPSIS
.IP \(bu
DESCRIPTION
.IP \(bu
OPTIONS
.IP \(bu
SEE ALSO
.IP \(bu
AUTHORS
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