Ubuntu Manpage: ppmtoxpm - convert a PPM image to an X11 pixmap

NAME

       ppmtoxpm - convert a PPM image to an X11 pixmap

SYNOPSIS

       ppmtoxpm [-name=xpmname] [-hexonly] [-rgb=rgb-textfile] [-alphamask=pgmfile] [ppmfile]

       Minimum  unique  abbreviation of option is acceptable.  You may use double hyphens instead
       of single hyphen to denote options.  You may use white space in place of the  equals  sign
       to separate an option name from its value.

DESCRIPTION

This program is part of Netpbm(1).

ppmtoxpm reads a PPM image as input and produces X11 pixmap (version 3) as output. This
format can be loaded by the XPM library.

In the XPM output, colors may be identified by name, such as "Red", or in hexadecimal, for
example "#FF0000". In the hexadecimal format, there may be from 1 through 4 hexadecimal
digits per RGB component.

By default, ppmtoxpbm tries to find a name for each color in the image in the system color
dictionary ⟨libppm.html#dictionary⟩ , and if it finds one, uses it. If it doesn't it uses
hexadecimal. You can force ppmtoxpbm to use hexadecimal only with the -hexonly option.
You can specify a different color dictionary with the -rgb option.

When ppmtoxpm uses the hexadecimal format for identifying a color, it uses the one that
uses the least number of hexadecimal digits that it takes to represent the maxval of the
input PPM. E.g. if the maxval of the input PPM is 100, ppmtoxpm uses 2 digits per
component, as in "#FF0000".

Some programs do not properly handle one-digit-per-component hexadecimal color specifiers.
They see the wrong colors. To produce an XPM that such a program can handle, make sure
the maxval of the input PPM is greater than 15, such as by running it through pamdepth
255.

Color Code Lengths - Image Size
In the XPM format, there is a palette ("color map") that assigns each color in the image
to a unique sequence of printable characters called a color code, and a raster that
identifies the color of each pixel of the image with one of those color codes. The length
of the color code affects the size of the image stream.

All color codes in an image are the same length, and ppmtoxpm tries to make it as short as
possible. That length is, of course, determined by the number of colors in the image.
ppmtoxpm counts the colors in the image, excluding those that will be transparent in the
output because of your transparency mask, and chooses a color code length accordingly.
There are 92 printable characters that can be used in a color code. Therefore, if you
have 92 or fewer colors, your color codes will be one character. If you have more than 92
but not more than 92 * 92, your color codes will be two characters. And so on.

There's one exception to the above: If you specify a transparency mask (the -alpha option,
one unique color code represents "transparent." This is true even if the transparency
mask doesn't actually produce any transparent pixels. So subtract one from the number of
possible colors if you use -alpha.

OPTIONS

In addition to the options common to all programs based on libnetpbm (most notably -quiet,
see
Common Options ⟨index.html#commonoptions⟩ ), ppmtoxpm recognizes the following command
line options:

-name=xpmname
This option specifies the prefix string which is specified in the resulting XPM
output. If you don't use the -name otpion, ppmtoxpm defaults to the filename
(without extension) of the ppmfile parameter. If you do not specify -name or
ppmfile (i.e. your input is from Standard Input), the prefix string defaults to the
string noname.

-hexonly
This option says never to put color names in the XPM file, but rather to identify
names by hexadecimal strings that explicitly identify RGB component intensities.
This means the reader of the file need not have access to a suitable color
dictionary to interpret it.

This option was introduced in Netpbm 10.15 (April 2003). Before that, it was the
default, overridden by specifying -rgb.

-rgb=rgb-textfile
This option names the file in which the color dictionary you want to use resides.
By default, ppmtoxpm uses the system color dictionary ⟨libppm.html#dictionary⟩ ,
and if it cannot open that file, uses hexadecimal color specifiers.

This option in meaningless when you specify -hexonly.

Before Netpbm 10.15 (April 2003), ppmtoxpm did not default to the system color
dictionary. If you didn't specify -rgb, ppmtoxpbm would use only hexadecimal color
specifiers.

-alphamask=pgmfile
This option names a PGM file to use as a transparency (alpha) mask. The file must
contain an image the same dimensions as the input image. ppmtoxpm marks as
transparent any pixel whose position in the transparency mask image is at most half
white.

If you don't specify -alphamask, ppmtoxpm makes all pixels in the output opaque.

ppmcolormask is one way to generate a transparency mask file. You might also
generate it by extracting transparency information from an XPM file with the
-alphaout option to xpmtoppm.

There are similar options on other Netpbm converters that convert from formats that
include transparency information too.

AUTHOR

       Copyright (C) 1990 by Mark W. Snitily.

       Permission to use, copy, modify, and distribute this software and  its  documentation  for
       any  purpose  and  without fee is hereby granted, provided that the above copyright notice
       appear in all copies and that both that copyright notice and this permission notice appear
       in supporting documentation.  This software is provided "as is" without express or implied
       warranty.

       This tool was developed for  Schlumberger  Technologies,  ATE  Division,  and  with  their
       permission  is  being  made  available  to  the public with the above copyright notice and
       permission notice.

       Upgraded to XPM2 by Paul Breslaw, Mecasoft SA,  Zurich,  Switzerland  (paul@mecazh.uu.ch),
       November 8, 1990.

       Upgraded to XPM version 3 by Arnaud Le Hors(lehors@mirsa.inria.fr), April 9, 1991.

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