1GIFTOOL(1) GIFLIB Documentation GIFTOOL(1)
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6 giftool - GIF transformation tool
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9 giftool [-a aspect] [-b bgcolor] [-d delaytime] [-i interlacing]
10 [-n imagelist] [-p left,top] [-s width,height] [-t transcolor]
11 [-u sort-flag] [-x disposal] [-z sort-flag]
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14 A filter for transforming GIFS. With no options, it's an expensive copy
15 of a GIF in standard input to standard output. Options specify
16 filtering operations and are performed in the order specified on the
17 command line.
18 The -n option selects images, allowing the tool to act on a subset of
20 images in a multi-image GIF. This option takes a comma-separated list
21 of decimal integers which are interpreted as 1-origin image indices;
22 these are the images that will be acted on. If no -n option is
23 specified, the tool will select and transform all images.
24 The -b option takes a decimal integer argument and uses it to set the
26 (0-origin) screen background color index.
27 The -f option accepts a printf-style format string and substitutes into
29 it the values of image-descriptor and graphics-control fields. The
30 string is formatted and output once for each selected image. Normal
31 C-style escapes \b, \f, \n, \r, \t. \v, and \xNN are interpreted; also
32 \e produces ESC (ASCII 0x1b). The following format cookies are
33 substituted:
34 %a
36 Pixel aspect byte.
37 %b
39 Screen background color.
40 %d
42 Image delay time
43 %h
45 Image height (y dimension)
46 %n
48 Image index
49 %p
51 Image position (as an x,y pair)
52 %s
54 Screen size (as an x,y pair)
55 %t
57 Image transparent-color index
58 %u
60 Image user-input flag (boolean)
61 %v
63 GIF version string
64 %w
66 Image width (x dimension)
67 %x
69 Image GIF89 disposal mode
70 %z
72 Image's color table sort flag (boolean, false if no local color
73 map)
74 Boolean substitutions may take a prefix to modify how they are
76 displayed:
77 1
79 "1" or "0"
80 o
82 "on" or "off"
83 t
85 "t" or "f"
86 y
88 "yes" or "no"
89 Thus, for example, "%oz" displays image sort flags using the strings
91 "on" and "off". The default with no prefix is numeric.
92 The -a option takes an unsigned decimal integer argument and uses it to
94 set the aspect-ratio bye in the logical screen descriptor block.
95 The -b option takes an unsigned decimal integer argument and uses it to
97 set the background color index in the logical screen descriptor block.
98 The -d option takes a decimal integer argument and uses it to set a
100 delay time, in hundredths of a second, on selected images.
101 The -i option sets or clears interlaccing in selected images.
103 Acceptable arguments are "1", "0", "yes", "no", "on", "off", "t", "f"
104 The -p option takes a (0-origin) x,y coordinate-pair and sets it as the
106 preferred upper-left-corner coordinates of selected images.
107 The -s option takes a (0-origin) x,y coordinate-pair and sets it as the
109 expected display screen size.
110 The -t option takes a decimal integer argument and uses it to set the
112 (0-origin) index of the transparency color in selected images.
113 The -u option sets or clears the user-input flag in selected images.
115 Acceptable arguments are "1", "0", "yes", "no", "on", "off", "t", "f".
116 The -x option takes a decimal integer argument and uses it to set the
118 GIF89 disposal mode in selected images.
119 The -z option sets or clears the color-table sort flag in selected
121 images. Acceptable arguments are "1", "0", "yes", "no", "on", "off",
122 "t", "f".
123 Note that the -a, -b, -p, -s, and -z options are included to complete
125 the ability to modify all fields defined in the GIF standard, but
126 should have no effect on how an image renders on browsers or modern
127 viewers.
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130 Eric S. Raymond.
131GIFLIB 3 June 2012 GIFTOOL(1)