CCITT Group 3
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{{FormatInfo | {{FormatInfo | ||
|formattype=electronic | |formattype=electronic | ||
| − | |subcat= | + | |subcat=Compression |
| + | |subcat2=Fax formats | ||
| + | |extensions={{ext|g3}} | ||
| + | |mimetypes={{mimetype|image/g3fax}} | ||
|pronom={{PRONOM|x-cmp/14}} | |pronom={{PRONOM|x-cmp/14}} | ||
}} | }} | ||
| − | '''CCITT Group 3''' is a lossless | + | '''CCITT Group 3''' is a lossless compressed data format for bi-level images. It is also known as '''T4''', '''T.4''', '''Fax3''', '''Group 3''', '''G3''', or '''ITU-T Fax Group 3'''. It is one of the formats used by [[fax machine]]s. It is usually embedded in another image file format such as [[TIFF]], but can be stored in a file by itself. |
| − | It comes in two main varieties: so-called '''1-dimensional''' and '''2-dimensional''' (though both are used on 2-dimensional images). | + | It comes in two main varieties: so-called '''1-dimensional''' and '''2-dimensional''' (though both are used on 2-dimensional images). The 1-dimensional variety uses [[Modified Huffman]] (MH) compression, and the 2-dimensional variety uses [[Modified READ]] (MR) compression. |
| − | + | ||
| − | The 1-dimensional variety uses [[Modified Huffman]] | + | |
| − | + | ||
| − | + | ||
== Related formats == | == Related formats == | ||
| − | + | Many of the formats listed in the [[Fax formats]] article use CCITT Group 3 compression. | |
| − | In | + | In a [[TIFF]] file, compression codes 2, 3, and 32771 are varieties of CCITT Group 3 compression. |
| + | |||
| + | Other formats that can use CCITT Group 3 compression include [[PDF]] and [[SPIFF]]. | ||
== See also == | == See also == | ||
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== Specifications == | == Specifications == | ||
| − | * [ | + | * [https://www.itu.int/rec/T-REC-T.4/en ITU-T Recommendation T.4] |
| − | * [ | + | * [https://www.adobe.io/open/standards/TIFF.html Adobe TIFF standards] → TIFF6.pdf, Section 10: Modified Huffman Compression - Defines a slightly simplified form of the 1-d format |
| + | |||
| + | == Software == | ||
| + | * [[Konvertor]] | ||
| + | * [[Netpbm]]: g3topbm, pbmtog3 | ||
| + | * [[ImageMagick]] (format named "FAX") | ||
| + | * [[Farbfeld Utilities]] | ||
| + | * [http://snisurset.net/code/abydos/ abydos] | ||
| + | |||
| + | == Sample files == | ||
| + | * {{DexvertSamples|image/faxGroup3}} | ||
| + | |||
| + | == Links == | ||
| + | * RFC 1494: Equivalences between 1988 X.400 and RFC-822 Message Bodies | ||
| + | * RFC 2159: A MIME Body Part for FAX | ||
| − | [[Category: | + | [[Category:Graphics]] |
| + | [[Category:Fax]] | ||
Latest revision as of 02:56, 28 December 2023
CCITT Group 3 is a lossless compressed data format for bi-level images. It is also known as T4, T.4, Fax3, Group 3, G3, or ITU-T Fax Group 3. It is one of the formats used by fax machines. It is usually embedded in another image file format such as TIFF, but can be stored in a file by itself.
It comes in two main varieties: so-called 1-dimensional and 2-dimensional (though both are used on 2-dimensional images). The 1-dimensional variety uses Modified Huffman (MH) compression, and the 2-dimensional variety uses Modified READ (MR) compression.
Contents |
[edit] Related formats
Many of the formats listed in the Fax formats article use CCITT Group 3 compression.
In a TIFF file, compression codes 2, 3, and 32771 are varieties of CCITT Group 3 compression.
Other formats that can use CCITT Group 3 compression include PDF and SPIFF.
[edit] See also
[edit] Specifications
- ITU-T Recommendation T.4
- Adobe TIFF standards → TIFF6.pdf, Section 10: Modified Huffman Compression - Defines a slightly simplified form of the 1-d format
[edit] Software
- Konvertor
- Netpbm: g3topbm, pbmtog3
- ImageMagick (format named "FAX")
- Farbfeld Utilities
- abydos
