File: gif2png.1

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gif2png 2.5.8-1
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'\" t
.\"     Title: gif2png
.\"    Author: [see the "AUTHORS" section]
.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
.\"      Date: 03/08/2012
.\"    Manual: Graphics
.\"    Source: gif2png
.\"  Language: English
.\"
.TH "GIF2PNG" "1" "03/08/2012" "gif2png" "Graphics"
.\" -----------------------------------------------------------------
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.nh
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.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
gif2png \- convert GIFs to PNGs
.SH "SYNOPSIS"
.HP \w'\fBgif2png\fR\ 'u
\fBgif2png\fR [\-bdfghinprsvwO] [\fIfile\&.[gif]\fR...]
.SH "DESCRIPTION"
.PP
The
\fBgif2png\fR
program converts files in the obsolescent Graphic Interchange Format (GIF) to Portable Network Graphics (PNG) format, an open W3C standard\&.
.PP
Normally
\fBgif2png\fR
converts each file named on the command line, leaving the original in place\&. If a name does not have a \&.gif extension, the unmodified name will be tried first, followed by the name with \&.gif appended\&. For each file named
foo\&.gif, a foo\&.png will be created\&.
.PP
When a multi\-image GIF file named
foo\&.gif
is converted, gif2png creates multiple PNG files, each containing one frame; their names will be
foo\&.png,
foo\&.p01,
foo\&.p02
etc\&.
.PP
If no source files are specified and stdin is a terminal,
\fBgif2png\fR
lists a usage summary and version information, then exits\&.
.PP
If no source files are specified, and stdin is a device or pipe, stdin is converted to
noname\&.png\&. (The program can\*(Aqt be a normal stdin\-to\-stdout filter because of the possibility that the input GIF might have multiple images)\&.
.PP
However, if filter mode is forced (with \-f) stdin will be converted to stdout, with
\fBgif2png\fR
returning an error code if the GIF is multi\-image\&.
.PP
The program will preserve the information contained in a GIF file as closely as possible, including GIF comment and application\-data extension blocks\&. All graphics data (pixels, RGB color tables) will be converted without loss of information\&. Transparency is also preserved\&. There is one exception; GIF plain\-text extensions are skipped\&.
.PP
The program automatically converts interlaced GIFs to interlaced PNGs\&. It detects images in which all colors are gray (equal R, G, and B values) and converts such images to PNG grayscale\&. Other images are converted to use the PNG palette type\&. Duplicate color entries are silently preserved\&. Unused color\-table entries cause an error message\&.
.PP
The action of the program can be modified with the following command\-line switches:
.PP
\fB\-b\fR {#}RRGGBB
.RS 4
Background\&. Replace transparent pixels with given RGB value, six hexadecimal digits interpreted as two hexits each of red, green, and blue value\&. The value may optionally be led with a #, HTML\-style\&.
.RE
.PP
\fB\-d \fR
.RS 4
Delete source GIF files after successful conversion\&.
.RE
.PP
\fB\-f \fR
.RS 4
Filter mode\&. Convert GIF on stdin to PNG on stdout, return error if the GIF is multi\-image\&.
.RE
.PP
\fB\-m \fR
.RS 4
Preserve file modification time\&. the PNG output gets the mod time of the input file, not the time it was converted\&.
.RE
.PP
\fB\-g \fR
.RS 4
Write gamma=1/2\&.2 and sRGB chunks in the PNG\&.
.RE
.PP
\fB\-h \fR
.RS 4
Generate PNG color\-frequency histogram chunks into converted color files\&.
.RE
.PP
\fB\-i \fR
.RS 4
Force conversion to interlaced PNG files\&.
.RE
.PP
\fB\-n \fR
.RS 4
Force conversion to non\-interlaced PNG files\&.
.RE
.PP
\fB\-p \fR
.RS 4
Display progress of PNG writing\&.
.RE
.PP
\fB\-r \fR
.RS 4
Try to recover data from corrupted GIF files\&.
.RE
.PP
\fB\-s \fR
.RS 4
Do not translate the GIF Software chunk to a PNG annotation\&.
.RE
.PP
\fB\-v \fR
.RS 4
Verbose mode; show summary line, \-vv enables conversion\-statistics and debugging messages\&.
.RE
.PP
\fB\-w \fR
.RS 4
Web\-probe switch; list GIFs that do not have multiple images to stdout\&. GIFs that fail this filter cause error messages to stderr\&.
.RE
.PP
\fB \-O \fR
.RS 4
Optimize; remove unused color\-table entries\&. Normally these trigger an error message and disable
\fB\-d\fR
(but conversion is completed anyway)\&. Also, use zlib compression level 9 (best compression) instead of the default level\&. The recovery algorithm enabled by
\fB\-r\fR
is as follows: Unused color table entries will not trigger an error message as they normally do, but will still be preserved unless
\fB\-O\fR
is also on, in which case they will be discarded\&. Missing color tables will be patched with a default that puts black at index 0, white at index 1, and supplies red, green, blue, yellow, purple and cyan as the remaining color values\&. Missing image pixels will be set to 0\&. Unrecognized or corrupted extensions will be discarded\&.
.RE
.SH "PROBLEMS"
.PP
Naively converting all your GIFs at one go with
\fBgif2png\fR
is not likely to give you the results you want\&. Animated GIFs cannot be translated to PNG, which is a single\-image format\&.
.PP
The web\-probe switch is intended to be used with scripts for converting web sites\&. In versions of this tool up to 2\&.5\&.2 it filtered out GIFs with transparency as well as GIFs with animations, but support for PNG transparency has been universal in browsers since about 2006\&.
.SH "STANDARDS AND SPECIFICATIONS"
.PP
Copies of the GIF89 specification are widely available on the Web; search for "GRAPHICS INTERCHANGE FORMAT"\&. The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated\&. GIF(sm) is a Service Mark property of CompuServe Incorporated\&. The GIF format was formerly covered by a blocking patent on LZW compression, but it expired in June 2003\&.
.PP
The PNG home site at <\m[blue]\fBhttp://www\&.libpng\&.org/pub/png/\fR\m[]> has very complete information on the PNG standard, PNG libraries, and PNG tools\&.
.SH "SEE ALSO"
.PP
web2png(1)
.SH "AUTHORS"
.PP
Code by Alexander Lehmann <alex@hal\&.rhein\-main\&.de>, 1995\&. Auto\-interlace conversion and tRNS optimization by Greg Roelofs <newt@pobox\&.com>, 1999\&. Man page, \-O, \-w, and production packaging by Eric S\&. Raymond <esr@thyrsus\&.com>, 1999\&. \-m option by Steve Ward, 2012\&.