Editing Run-length encoding (section)

==History and applications==

Run-length encoding (RLE) schemes were employed in the transmission of analog television signals as far back as 1967.<ref name="robinson" /> In 1983, run-length encoding was [[patent]]ed by [[Hitachi]].<ref>{{cite web |date=21 March 1996 |title=Run Length Encoding Patents |url=http://www.ross.net/compression/patents_notes_from_ccfaq.html |access-date=14 July 2019 |publisher=Internet FAQ Consortium}}</ref><ref>{{cite web |date=7 August 1984 |title=Method and system for data compression and restoration |url=https://patents.google.com/patent/US4586027A |access-date=14 July 2019 |website=[[Google Patents]]}}</ref><ref>{{cite web |date=8 August 1983 |title=Data recording method |url=https://patents.google.com/patent/JPH0828053B2/en |access-date=14 July 2019 |website=[[Google Patents]]}}</ref> RLE is particularly well suited to [[Palette (computing)|palette]]-based bitmap images (which use relatively few colours) such as [[computer icons]], and was a popular image compression method on early [[online service]]s such as [[CompuServe]] before the advent of more sophisticated formats such as [[GIF]].<ref name="transactor" />  It does not work well on continuous-tone images (which use very many colours) such as photographs, although [[JPEG]] uses it on the coefficients that remain after transforming and [[Quantization (image processing)|quantizing]] image blocks.

Common formats for run-length encoded data include [[Truevision TGA]], [[PackBits]] (by Apple, used in [[MacPaint]]), [[PCX]] and [[ILBM]].  The [[International Telecommunication Union]] also describes a standard to encode run-length colour for [[fax]] machines, known as T.45.<ref name="itu" />  That fax colour coding standard, which along with other techniques is incorporated into [[Modified Huffman coding]],{{citation needed|date=December 2015}} is relatively efficient because most faxed documents are primarily white space, with occasional interruptions of black.