Editing Raster graphics (section)

===Displays===
{{main | Electronic television |Computer monitor}}

Early [[mechanical television]]s developed in the 1920s employed rasterization principles. [[Electronic television]] based on [[cathode-ray tube]] displays are [[raster scan]]ned with horizontal rasters painted left to right, and the raster lines painted top to bottom. 

Modern flat-panel displays such as LED monitors still use a raster approach. Each on-screen pixel directly corresponds to a small number of bits in memory.<ref>{{cite web|url=http://foldoc.org/bitmap+display|title=bitmap display |publisher=FOLDOC |date=2002-05-15 |access-date=30 November 2014|archive-date=16 June 2018|archive-url=https://web.archive.org/web/20180616103833/http://foldoc.org/bitmap+display|url-status=live}}</ref> The screen is refreshed simply by scanning through pixels and coloring them according to each set of bits. The refresh procedure, being speed critical, is often implemented by dedicated circuitry, often as a part of a [[graphics processing unit]]. 

Using this approach, the computer contains an area of memory that holds all the data that are to be displayed. The central processor writes data into this region of memory and the video controller collects them from there. The bits of data stored in this block of memory are related to the eventual pattern of pixels that will be used to construct an image on the display.<ref>Murray, Stephen. "[https://link-gale-com.libaccess.lib.mcmaster.ca/apps/doc/CX3401200218/GVRL?u=ocul_mcmaster&sid=GVRL&xid=acaf5d43 Graphic Devices]". ''Computer Sciences'', edited by Roger R. Flynn, vol. 2: Software and Hardware, Macmillan Reference USA, 2002, pp. 81–83. ''Gale eBooks''. Accessed 3 Aug. 2020.</ref>

An early scanned display with raster computer graphics was invented in the late 1960s by A. Michael Noll at [[Bell Labs]],<ref>{{cite journal |first=A. Michael |last=Noll |title=Scanned-Display Computer Graphics |journal=Communications of the ACM |volume=14 |issue=3 |pages=143–150 |date=March 1971 |doi=10.1145/362566.362567|s2cid=2210619 |doi-access=free }}</ref> but its patent application filed February 5, 1970, was abandoned at the Supreme Court in 1977 over the issue of the patentability of computer software.<ref>{{cite web|url=http://noll.uscannenberg.org/Patents.htm|title=Patents|publisher=Noll.uscannenberg.org|access-date=30 November 2014|archive-date=22 February 2014|archive-url=https://web.archive.org/web/20140222131415/http://noll.uscannenberg.org/Patents.htm|url-status=live}}</ref>