GIFTOOL(1) GIFLIB Documentation GIFTOOL(1)NAMEgiftool - GIF transformation tool
SYNOPSISgiftool [-a aspect] [-b bgcolor] [-d delaytime] [-i interlacing]
[-n imagelist] [-p left,top] [-s width,height] [-t transcolor]
[-u sort-flag] [-x disposal] [-z sort-flag]
DESCRIPTION
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.
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.
The -b option takes a decimal integer argument and uses it to set the
(0-origin) screen background color index.
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:
%a
Pixel aspect byte.
%b
Screen background color.
%d
Image delay time
%h
Image height (y dimension)
%n
Image index
%p
Image position (as an x,y pair)
%s
Screen size (as an x,y pair)
%t
Image transparent-color index
%u
Image user-input flag (boolean)
%v
GIF version string
%w
Image width (x dimension)
%x
Image GIF89 disposal mode
%z
Image's color table sort flag (boolean, false if no local color
map)
Boolean substitutions may take a prefix to modify how they are
displayed:
1
"1" or "0"
o
"on" or "off"
t
"t" or "f"
y
"yes" or "no"
Thus, for example, "%oz" displays image sort flags using the strings
"on" and "off". The default with no prefix is numeric.
The -a option takes an unsigned decimal integer argument and uses it to
set the aspect-ratio bye in the logical screen descriptor block.
The -b option takes an unsigned decimal integer argument and uses it to
set the background color index in the logical screen descriptor block.
The -d option takes a decimal integer argument and uses it to set a
delay time, in hundredths of a second, on selected images.
The -i option sets or clears interlaccing in selected images.
Acceptable arguments are "1", "0", "yes", "no", "on", "off", "t", "f"
The -p option takes a (0-origin) x,y coordinate-pair and sets it as the
preferred upper-left-corner coordinates of selected images.
The -s option takes a (0-origin) x,y coordinate-pair and sets it as the
expected display screen size.
The -t option takes a decimal integer argument and uses it to set the
(0-origin) index of the transparency color in selected images.
The -u option sets or clears the user-input flag in selected images.
Acceptable arguments are "1", "0", "yes", "no", "on", "off", "t", "f".
The -x option takes a decimal integer argument and uses it to set the
GIF89 disposal mode in selected images.
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".
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.
AUTHOR
Eric S. Raymond.
GIFLIB 3 June 2012 GIFTOOL(1)
