1GIFBUILD(1) GIFLIB Documentation GIFBUILD(1)
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6 gifbuild - dump GIF data in a textual format, or undump it to a GIF
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9 gifbuild [-v] [-a] [-d] [-t translation-table] [-h] [gif-file]
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12 A program to convert a series of editable text GIF icon specifications
13 and named GIF files into a multi-image GIF, usable as a graphic
14 resource file. It can also dump existing GIFs in this format. When
15 dumping a GIF, certain sanity checks are performed which may result in
16 a warning emitted to standard error.
17 If no GIF file is given, gifbuild will try to read a text input from
19 stdin.
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22 Here is a syntax summary in informal BNF. The token `NL' represents a
23 required newline.
24 <gif-spec> ::= <header-block> <image-block>...
26 <header-block> ::= <header-declaration>...
28 <header-declaration ::=
30 | screen width <digits> NL
31 | screen height <digits> NL
32 | screen colors <digits> NL
33 | screen background <digits> NL
34 | pixel aspect byte <digits> NL
35 | screen map <color-table> NL
36 <color-table> ::= <color-declaration>... end NL
38 <color-declaration> ::= rgb <digits> <digits> <digits> [ is <key>] NL
40 | sort flag {on|off} NL
41 <image-block> ::= include <file-name> NL
43 | image NL
44 <image-declaration>...
45 <raster-picture>
46 [ <extension> ]
47 <image-declarations> ::= image top <digits> NL
49 | image left <digits> NL
50 | image interlaced NL
51 | image map <color-table> NL
52 | image bits <digits> by <digits> [hex|ascii] NL <raster-block>
53 <extension> := <comment> NL <extension-block> NL end NL
55 | <plaintext> NL <extension-block> NL end NL
56 | graphics control NL <GCB-part> NL end NL
57 | netscape loop <digits> NL
58 | extension <hex-digits> NL <extension-block> NL end NL
59 <GCB-part> ::= disposal mode <digits> NL
61 | user input flag {on|off} NL
62 | delay <digits> NL
63 | transparent index <digits> NL
64 If the data types of the “screen height”, “screen width”, “screen
67 background”, “image top”, and “image left” declarations aren't obvious
68 to you, what are you doing with this software?
69 The “pixel aspect byte” declaration sets an integer denominator for a
71 fraction expressing the puxel aspect ratio. See the GIF standard for
72 details; this field is actually long obsolete.
73 A color table declares color indices (in ascending order from 0) and
75 may associate them with key characters (these associations are absent
76 when the map is more than 94 colors lang and raster blocks using it
77 must use hex pairs). These characters can later be used in raster
78 blocks. As these must be printable and non-whitespace, you can only
79 specify 94 colors per icon. Life is like that sometimes.
80 A color table declaration can also set the table's sort flag with "sort
82 flag on" or "sort flag off" on any line before the end.
83 An “ascii” raster block is just a block of key characters (used for a
85 color map of 94 or fewer colors). A “hex” raster block uses hex digit
86 pairs instead (used for a color map with more than 94 colors). The
87 default is ASCII. It should be sized correctly for the “image bits”
88 declaration that leads it. Raster blocks from interlaced GIFs are
89 dumped with the lines in non-interlaced order.
90 The “comment”, “plaintext” or “ggraphics control” keywords lead defined
92 GIF89 extension record data. The final GIF89 type, graphics control and
93 application block, are not yet supported, but the code does recognize a
94 Netscape loop block. You can also say “extension” followed by a
95 hexadecimal record type. All of these extension declarations must be
96 followed by an extension block, which is terminated by the keyword
97 “end” on its own line.
98 An extension block is a series of text lines, each interpreted as a
100 string of bytes to fill an extension block (the terminating newline is
101 stripped). Text may include standard C-style octal and hex escapes
102 preceded by a backslash.
103 A graphics control block declaration creates a graphics control
105 extension block; for the field semantics see the GIF89 standard, part
106 23.
107 A netscape loop declaration creates an application extension block
109 containing a NETSCAPE 2.0 animation loop control with a specified
110 repeat count (repeat count 0 means loop forever). This must be
111 immediately after the header declaration. These loop blocks are
112 interpreted by the Netscape/Mozilla/Firefox line of browsers.
113 All <digits> tokens are interpreted as decimal numerals; <hex-digits>
115 tokens are interpreted as two hex digits (a byte). All coordinates are
116 zero-origin with the top left corner (0,0). Range checking is weak and
117 signedness checking nonexistent; caveat hacker!
118 In general, the amount of whitespace and order of declarations within a
120 header or image block is not significant, except that a raster picture
121 must immediately follow its “image bits” bits declaration.
122 The “include” declaration includes a named GIF as the next image. The
124 global color maps of included GIFs are merged with the base table
125 defined by any “screen color” declaration. All images of an included
126 multi-image GIF will be included in order.
127 Comments (preceded with “#”) will be ignored.
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131 -v
132 Verbose mode (show progress). Enables printout of running scan
133 lines.
134 -d
136 Dump the input GIF file(s) into the text form described above.
137 -t
139 Specify name characters to use when dumping raster blocks. Only
140 valid with -d option.
141 -h
143 Print one line of command line help, similar to Usage above.
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146 Error checking is rudimentary.
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149 A sample icon file called sample.ico is included in the pic directory
150 of the GIFLIB source distribution.
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153 Eric S. Raymond <esr@thyrsus.com>
154GIFLIB 2 May 2012 GIFBUILD(1)