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<refentry id='giftool.1'>
<refentryinfo><date>3 June 2012</date></refentryinfo>
<refmeta>
<refentrytitle>giftool</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="source">GIFLIB</refmiscinfo>
<refmiscinfo class="manual">GIFLIB Documentation</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>giftool</refname>
<refpurpose>GIF transformation tool</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>
<cmdsynopsis>
<command>giftool</command>
<arg choice='opt'>-a <replaceable>aspect</replaceable></arg>
<arg choice='opt'>-b <replaceable>bgcolor</replaceable></arg>
<arg choice='opt'>-d <replaceable>delaytime</replaceable></arg>
<arg choice='opt'>-i <replaceable>interlacing</replaceable></arg>
<arg choice='opt'>-n <replaceable>imagelist</replaceable></arg>
<arg choice='opt'>-p <replaceable>left,top</replaceable></arg>
<arg choice='opt'>-s <replaceable>width,height</replaceable></arg>
<arg choice='opt'>-t <replaceable>transcolor</replaceable></arg>
<arg choice='opt'>-u <replaceable>sort-flag</replaceable></arg>
<arg choice='opt'>-x <replaceable>disposal</replaceable></arg>
<arg choice='opt'>-z <replaceable>sort-flag</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1><title>Description</title>
<para>A filter for transforming GIFS. With no options, it's an expensive
copy of a GIF in standard input to standard output. Options specify
filtering operations and are performed in the order specified on the command
line.</para>
<para>The -n option selects images, allowing the tool to act on a
subset of images in a multi-image GIF. This option takes a
comma-separated list of decimal integers which are interpreted as
1-origin image indices; these are the images that will be acted on.
If no -n option is specified, the tool will select and transform all
images.</para>
<para>The -b option takes a decimal integer argument and uses it to
set the (0-origin) screen background color index.</para>
<para>The -f option accepts a printf-style format string and
substitutes into it the values of image-descriptor and graphics-control
fields. The string is formatted and output once for each selected
image. Normal C-style escapes \b, \f, \n, \r, \t. \v, and \xNN are
interpreted; also \e produces ESC (ASCII 0x1b). The following format
cookies are substituted:</para>
<variablelist>
<varlistentry>
<term>%a</term>
<listitem><para>Pixel aspect byte.</para></listitem>
</varlistentry>
<varlistentry>
<term>%b</term>
<listitem><para>Screen background color.</para></listitem>
</varlistentry>
<varlistentry>
<term>%d</term>
<listitem><para>Image delay time</para></listitem>
</varlistentry>
<varlistentry>
<term>%h</term>
<listitem><para>Image height (y dimension)</para></listitem>
</varlistentry>
<varlistentry>
<term>%n</term>
<listitem><para>Image index</para></listitem>
</varlistentry>
<varlistentry>
<term>%p</term>
<listitem><para>Image position (as an x,y pair)</para></listitem>
</varlistentry>
<varlistentry>
<term>%s</term>
<listitem><para>Screen size (as an x,y pair)</para></listitem>
</varlistentry>
<varlistentry>
<term>%t</term>
<listitem><para>Image transparent-color index</para></listitem>
</varlistentry>
<varlistentry>
<term>%u</term>
<listitem><para>Image user-input flag (boolean)</para></listitem>
</varlistentry>
<varlistentry>
<term>%v</term>
<listitem><para>GIF version string</para></listitem>
</varlistentry>
<varlistentry>
<term>%w</term>
<listitem><para>Image width (x dimension)</para></listitem>
</varlistentry>
<varlistentry>
<term>%x</term>
<listitem><para>Image GIF89 disposal mode</para></listitem>
</varlistentry>
<varlistentry>
<term>%z</term>
<listitem><para>Image's color table sort flag (boolean,
false if no local color map)</para></listitem>
</varlistentry>
</variablelist>
<para>Boolean substitutions may take a prefix to modify how they are
displayed:</para>
<variablelist>
<varlistentry>
<term>1</term>
<listitem><para>"1" or "0"</para></listitem>
</varlistentry>
<varlistentry>
<term>o</term>
<listitem><para>"on" or "off"</para></listitem>
</varlistentry>
<varlistentry>
<term>t</term>
<listitem><para>"t" or "f"</para></listitem>
</varlistentry>
<varlistentry>
<term>y</term>
<listitem><para>"yes" or "no"</para></listitem>
</varlistentry>
</variablelist>
<para>Thus, for example, "%oz" displays image sort flags using the
strings "on" and "off". The default with no prefix is numeric.</para>
<para>The -a option takes an unsigned decimal integer argument and
uses it to set the aspect-ratio bye in the logical screen descriptor
block.</para>
<para>The -b option takes an unsigned decimal integer argument and
uses it to set the background color index in the logical screen
descriptor block.</para>
<para>The -d option takes a decimal integer argument and uses it to set a delay
time, in hundredths of a second, on selected images.</para>
<para>The -i option sets or clears interlaccing in selected images. Acceptable arguments are "1", "0", "yes", "no", "on", "off", "t", "f"</para>
<para>The -p option takes a (0-origin) x,y coordinate-pair and sets it
as the preferred upper-left-corner coordinates of selected
images.</para>
<para>The -s option takes a (0-origin) x,y coordinate-pair and sets it
as the expected display screen size.</para>
<para>The -t option takes a decimal integer argument and uses it to set the
(0-origin) index of the transparency color in selected images.</para>
<para>The -u option sets or clears the user-input flag in selected
images. Acceptable arguments are "1", "0", "yes", "no", "on", "off",
"t", "f".</para>
<para>The -x option takes a decimal integer argument and uses it to set the
GIF89 disposal mode in selected images.</para>
<para>The -z option sets or clears the color-table sort flag in
selected images. Acceptable arguments are "1", "0", "yes", "no",
"on", "off", "t", "f".</para>
<para>Note that the -a, -b, -p, -s, and -z options are included to
complete the ability to modify all fields defined in the GIF standard,
but should have no effect on how an image renders on browsers or
modern viewers.</para>
</refsect1>
<refsect1><title>Author</title>
<para>Eric S. Raymond.</para>
</refsect1>
</refentry>