View source for JBIG

{{Short description|Image file format}}
{{about|the bi-level image compression scheme|its designers|Joint Bi-level Image Experts Group}}
{{Infobox file format
|         icon = 
|    extension = .jbg, .jbig
|         mime = 
|    type code =
|  creatorcode =
|        owner = [[International Organization for Standardization|ISO]], [[International Electrotechnical Commission|IEC]], [[ITU-T]]
|     released = 1993
|        genre = [[Image file formats]]
| containerfor = 
|  containedby = 
| extendedfrom = 
|   extendedto = [[JBIG2]]
|    standards = ISO/IEC 11544, ITU-T Recommendations T.82, T.85
}}

'''JBIG''' is an early [[Lossless data compression|lossless]] [[image compression]] standard from the [[Joint Bi-level Image Experts Group]], standardized as [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] standard 11544 and as [[ITU-T]] recommendation T.82 in March 1993.<ref name="standards">{{cite book
|first1=Shahriar
|title=Digital Video Concepts, Methods, and Metrics
|publisher=Apress
|year=2014
|pages=55–100
|isbn=978-1-4302-6712-6
|doi=10.1007/978-1-4302-6713-3_3
|chapter=Video Coding Standards
|last1=Akramullah
}}</ref> It is widely implemented in fax machines. Now that the newer [[binary image|bi-level image]] compression standard [[JBIG2]] has been released, JBIG is also known as '''JBIG1'''. JBIG was designed for compression of binary images, particularly for [[fax]]es, but can also be used on other images. In most situations JBIG offers between a 20% and 50% increase in compression efficiency over [[Group 4 compression|Fax Group 4 compression]], and in some situations, it offers a 30-fold improvement.

JBIG is based on a form of [[arithmetic coding]] developed by [[IBM]] (known as the Q-coder) that also uses a relatively minor refinement developed by [[Mitsubishi]], resulting in what became known as the QM-coder. It bases the probability estimates for each encoded bit on the values of the previous bits and the values in previous lines of the picture. JBIG also supports progressive transmission, which generally incurs a small overhead in bit rate (around 5%).

== Patents ==
Doubts about patent licence requirements for JBIG1 implementations by IBM, Mitsu{{shy}}bishi and AT&T prevented the codec from being widely implemented in open-source software.<ref name=Kuhn/> For example, as of 2012, none of the commonly used web browsers supported it. Since 2012, there are now no more JBIG1 patents in force – the last ones to expire were Mitsubishi's patents in Canada and Australia (on 25 February 2011) and in the United States (on 4 April 2012).<ref name=Kuhn>{{Cite web|url=https://www.cl.cam.ac.uk/~mgk25/jbigkit/patents/|title=JBIG1 patent information|website=www.cl.cam.ac.uk}}</ref><ref>{{Cite web|url=http://www.patentlens.net/patentlens/structured.cgi?patnum=US%2F5404140|title=archive.ph|website=archive.ph|access-date=2023-01-21|archive-date=2013-02-22|archive-url=https://archive.today/20130222004619/http://www.patentlens.net/patentlens/structured.cgi?patnum=US/5404140|url-status=bot: unknown}}</ref>

==See also==
* [[ISO/IEC JTC 1/SC 29]]
* [[JBIG2]]

==References==
{{reflist}}

== External links ==
* [http://www.cl.cam.ac.uk/~mgk25/jbigkit/ JBIG-KIT] &ndash; a [[free software|free]] [[C (programming language)|C]] implementation of the JBIG encoder and decoder
* [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=19498 ISO/IEC 11544]
* ITU-T Recommendations [http://www.itu.int/rec/T-REC-T.82 T.82], [http://www.itu.int/rec/T-REC-T.85 T.85]
* {{IETF RFC|2879|link=no}} – Content Feature Schema for Internet Fax (V2)
* {{IETF RFC|3949|link=no}} – File Format for Internet Fax

{{ISO standards}}
{{List of International Electrotechnical Commission standards}}
{{Graphics file formats}}
{{Compression formats}}

[[Category:JBIG| ]]
[[Category:Lossless compression algorithms]]
[[Category:Lossy compression algorithms]]
[[Category:Graphics file formats]]
[[Category:ITU-T recommendations|T.82]]
[[Category:ISO standards]]
[[Category:IEC standards]]
[[Category:Image compression]]