199 lines
5.0 KiB
HTML
199 lines
5.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of giftopnm</TITLE>
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</HEAD><BODY>
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<H1>giftopnm</H1>
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Section: User Commands (1)<BR>Updated: 13 January 2001<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="ixAAB"></A>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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giftopnm - convert a GIF file into a portable anymap
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>giftopnm</B>
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[<B>--alphaout=</B>{<I>alpha-filename</I>,<B>-</B>}]
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[<B>-verbose</B>]
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[<B>-comments</B>]
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[<B>-image</B>
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<I>N</I>]
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[<I>GIFfile</I>]
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<P>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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This is a graphics format converter from the GIF format to the PNM
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(i.e. PBM, PGM, or PPM) format.
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<P>
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If the image contains only black and maximally bright white, the output
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is PBM. If the image contains more than those two colors, but only grays,
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the output is PGM. If the image contains other colors, the output is PPM.
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<P>
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If you have an animated GIF file, you can extract individual frames from it
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with
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<B>gifsicle</B>
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and then convert those using
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<B>giftopnm</B>.
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<A NAME="ixAAC"></A>
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<P>
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A GIF image contains rectangular pixels. They all have the same
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aspect ratio, but may not be square (it's actually quite unusual for
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them not to be square, but it could happen). The pixels of a Netpbm
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image are always square. Because of the engineering complexity to
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do otherwise,
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<B>giftopnm</B>
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converts a GIF image to a Netpbm image pixel-for-pixel.
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This means if the GIF pixels are not square, the Netpbm output image has
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the wrong aspect ratio. In this case,
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<B>giftopnm</B>
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issues an informational message telling you to run
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<B>pnmscale</B>
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to correct the output.
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<P>
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<A NAME="lbAE"> </A>
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<H2>OPTIONS</H2>
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<DL COMPACT>
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<DT id="1"><B>--alphaout=</B><I>alpha-filename</I>
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<DD>
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<B>giftopnm </B>
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creates a PGM (portable graymap) file containing the alpha channel
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values in the input image. If the input image doesn't contain an alpha
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channel, the
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<I>alpha-filename</I>
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file contains all zero (transparent) alpha values. If you don't specify
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<B>--alphaout</B>,
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<B>giftopnm</B>
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does not generate an alpha file, and if the input image has an alpha channel,
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<B>giftopnm</B>
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simply discards it.
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<P>
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If you specify
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<B>-</B>
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as the filename,
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<B>giftopnm</B>
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writes the alpha output to Standard Output and discards the image.
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<P>
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See
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<B><A HREF="/cgi-bin/man/man2html?1+pnmcomp">pnmcomp</A></B>(1)
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for one way to use the alpha output file.
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<DT id="2"><B>-verbose</B>
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<DD>
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Produce verbose output about the GIF file input.
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<DT id="3"><B>-comments</B>
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<DD>
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Only output GIF89 comment fields.
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<DT id="4"><B>-image </B><I>N</I>
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<DD>
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Output the specified gif image from the input GIF archive (where
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<I>N</I>
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is '1', '2', '20'...).
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Normally there is only one image per file, so this option
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is not needed.
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</DL>
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<P>
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All flags can be abbreviated to their shortest unique prefix.
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<P>
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<A NAME="lbAF"> </A>
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<H2>RESTRICTIONS</H2>
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This does not correctly handle the Plain Text Extension of the GIF89
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standard, since I did not have any example input files containing them.
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<P>
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<A NAME="lbAG"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+ppmtogif">ppmtogif</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+ppmcolormask">ppmcolormask</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+pnmcomp">pnmcomp</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+gifsicle">gifsicle</A></B>(1)
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<<A HREF="http://www.lcdf.org/gifsicle">http://www.lcdf.org/gifsicle</A>>,
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<B><A HREF="/cgi-bin/man/man2html?5+ppm">ppm</A></B>(5).
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<A NAME="lbAH"> </A>
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<H2>AUTHOR</H2>
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Copyright (c) 1993 by David Koblas (<A HREF="mailto:koblas@netcom.com">koblas@netcom.com</A>)
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<P>
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<A NAME="lbAI"> </A>
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<H2>LICENSE</H2>
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If you use
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<B>giftopnm</B>,
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you are using a patent on the LZW compression method which is owned by
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Unisys, and in all probability you do not have a license from Unisys
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to do so. Unisys typically asks $5000 for a license for trivial use
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of the patent. Unisys has never enforced the patent against trivial
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users, and has made statements that it is much less concerned about
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people using the patent for decompression (which is what
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<B>giftopnm</B>
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does than for compression. The patent expires in 2003 / 2004, depending on
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the country.
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<P>
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Rumor has it that IBM also owns a patent covering
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<B>giftopnm</B>.
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<P>
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A replacement for the GIF format that does not require any patents to use
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is the PNG format.
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">OPTIONS</A><DD>
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<DT id="9"><A HREF="#lbAF">RESTRICTIONS</A><DD>
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<DT id="10"><A HREF="#lbAG">SEE ALSO</A><DD>
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<DT id="11"><A HREF="#lbAH">AUTHOR</A><DD>
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<DT id="12"><A HREF="#lbAI">LICENSE</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:13 GMT, March 31, 2021
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</BODY>
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