Editing Spatial anti-aliasing (section)

==Anti-aliasing and gamma compression==

Digital images are usually stored in a [[Gamma compression|gamma-compressed]] format, but most optical anti-aliasing filters are linear. So to down-sample an image in a way that would match optical blurring, one should first convert it to a linear format, then apply the anti-aliasing filter, and finally convert it back to a gamma compressed format.<ref>{{Cite journal|last1=Maruszczyk|first1=Kuba|last2=Denes|first2=Gyorgy|last3=Mantiuk|first3=Rafal K.|date=2018|title=Improving Quality of Anti-Aliasing in Virtual Reality|url=http://pdfs.semanticscholar.org/09e2/3e0d23bc641642ff57cc6fa2d6c741ae4bbe.pdf|archive-url=https://web.archive.org/web/20190218080915/http://pdfs.semanticscholar.org/09e2/3e0d23bc641642ff57cc6fa2d6c741ae4bbe.pdf|url-status=dead|archive-date=2019-02-18|journal=EG UK Computer Graphics & Visual Computing|s2cid=54081570}}</ref> Using linear arithmetic on a gamma-compressed image results in values which are slightly different from the ideal filter. This error is larger when dealing with high contrast areas, causing high contrast areas to become dimmer: bright details (such as a cat's whiskers) become visually thinner, and dark details (such as tree branches) become thicker, relative to the optically anti-aliased image.<ref>{{cite web |first=Eric |last=Brasseur |url=http://www.4p8.com/eric.brasseur/gamma.html |title=Gamma error in picture scaling |website=www.4p8.com |access-date=2012-12-14 |url-status=dead |archive-url=https://web.archive.org/web/20121223021721/http://www.4p8.com/eric.brasseur/gamma.html |archive-date=2012-12-23 }}</ref> Each pixel is individually distorted, meaning outlines become unsmooth after anti-aliasing. Because the conversion to and from a linear format greatly slows down the process, and because the differences are usually subtle, most [[image editing software]], including [[Final Cut Pro]] and [[Adobe Photoshop]], process images in the gamma-compressed domain.

Most modern [[GPU]]s support storing [[Texture mapping|textures]] in memory in [[sRGB]] format, and can perform transformation to linear space and back transparently, with essentially no loss in performance.