\." Manual page for xcf2png
\." Copyright (C) 2006  Henning Makholm
\."
\." This program is free software; you can redistribute it and/or modify
\." it under the terms of version 2 of the GNU General Public License as
\." published by the Free Software Foundation.
\."
\." This program is distributed in the hope that it will be useful,
\." but WITHOUT ANY WARRANTY; without even the implied warranty of
\." MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
\." GNU General Public License for more details.
\."
\." You should have received a copy of the GNU General Public License
\." along with this program; if not, write to the Free Software
\." Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
.TH xcf2png 1 2006-01-25 "Xcftools" ""
.SH NAME
xcf2png \- convert from GIMP xcf files to png format
.SH SYNOPSIS
.B xcf2png
[
.I options
]
.I filename
[
.I layer names
]
.SH DESCRIPTION
.B xcf2png
is a command-line tool that converts image files in the XCF format used by
.BR gimp (1)
to the generic image format
.BR png ,
.BR ppm (5),
flattening layers if necessary. It does not need to have
the Gimp engine itself available.
.SH GENERAL OPTIONS
.so xcf2png.1i
.P
Several groups of options are mutually incompatible; in each group the
one given last will win:
.TP 4
1)
.B \-A
and
.BR \-b .
.TP
2)
.BR \-g and
.BR \-m .
.TP
3)
.B \-D
and
.BR \-G .
.TP
4)
.BR \-j ,
.BR \-z ,
and
.BR \-Z .
.SH LAYER SPECIFICATIONS
If no
.I layer name
is given on the command line, all of the visible layers in
the XCF file are merged to produce the output image.
It is also possible to specify the layers to merge explicitly,
by giving their names as separate arguments after the
input filename. In that case, the output will contain
.I only
the named layers. The layers will be merged in the order
they appear on the command line, with the leftmost being
"at the bottom" \- that is, the layer ordering in the XCF file
will be ignored.
.P
The following options can be given
.I after
a layer name to override the global properties of the layer:
.so xcf2png.1il
.SH EXIT STATUS
The exit status of
.B xcf2png
is
.TP 5
0
Success
.TP
20
Problems parsing the command line, including unknown color names
(or missing color name directory) for
.BR \-b .
.TP
21
The specified XCF file does not exist or cannot be read.
.TP
22
A layer named on the command line was not found, or the
.B --mask
option was used for a layer that has no layer mask.
.TP
102
The
.B \-G
option was given, yet partial transparency was found.
.TP
103
.B \-g
was given, yet colored
pixels were found.
.TP
123
The XCF file contains presumably valid features that
.B xcftools
does not support. (Certain layer modes, for example, cause
this return).
.TP
125
The XCF file is malformed.
.TP
126
An uncompression program could not be executed or terminated
abnormally.
.TP
127
Unexpected I/O error, internal errors, or other "this can't happen"
situations.
.P
If an uncompression program returns an error exit status, this will
be returned from
.B xcf2png
too.
.SH BUGS AND LIMITATIONS
.P
When several partially transparent layers are merged, the pixel
values are interpolated without gamma correction. (The Gimp also
does it this way). Some slight rounding errors in the interpolation
are inevitable;
.B xcf2png
sometimes have different rounding errors than the Gimp itself,
especially when more than two layers are involved, or in case of
some of the more exotic layer modes.
These differences are usually not visible to the eye.
.P
A few particularly exotic layer modes (which work in HSV space rather
than RGB space) are not currently implemented.
.P
There are probably other bugs lurking in corner cases. If you discover
one, please notify the author.

.SH FILES
.TP 8
.B /usr/lib/X11/rgb.txt
Color name database for
.BR \-b .
.SH AUTHOR
.B xcf2pnm
was written by Henning Makholm <henning@makholm.net>
.P
.SH SEE ALSO
.BR xcfinfo (1),
.BR xcf2pnm (1)