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

Provided by: netpbm_11.10.02-1build1_amd64

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 ,
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 ), 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 , 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.

DOCUMENT SOURCE