Editing Gamma correction (section)

==Gamma meta information==
{{Further|Color management#Application level}}

Some picture formats allow an image's intended gamma (of transformations between encoded image samples and light output) to be stored as [[metadata]], facilitating automatic gamma correction. The [[Portable Network Graphics|PNG]] specification includes the gAMA chunk for this purpose<ref>{{cite web |url=https://www.w3.org/TR/PNG |title=Portable Network Graphics (PNG) Specification (Second Edition) |publisher=[[World Wide Web Consortium]] |website=www.w3.org |access-date=2020-01-25}}</ref> and with formats such as [[JPEG]] and [[TIFF]] the [[Exif]] Gamma tag can be used. Some formats can specify the ICC profile which includes a transfer function.

These features have historically caused problems, especially on the web. For HTML and CSS colors and JPG or GIF images without attached color profile metadata, popular browsers passed numerical color values to the display without color management, resulting in substantially different appearance between devices; however those same browsers sent images with gamma explicitly set in metadata through color management, and also applied a default gamma to PNG images with metadata omitted. This made it impossible for PNG images to simultaneously match HTML or untagged JPG colors on every device.<ref>{{cite web |url=https://hsivonen.fi/png-gamma/ |title=The Sad Story of PNG Gamma "Correction" |last=Sivonen |first=Henri |website=hsivonen.fi |date=2010-03-31 |access-date=2021-01-25}}</ref><ref>{{cite web|url=https://jonathannicol.com/blog/2006/12/01/fixing-png-gamma/|title=Fixing PNG Gamma|date=December 2006 |last= Nicol |first= Jonathan }}</ref><ref>{{cite web |url=http://www.libpng.org/pub/png/colorcube/gamma-consistency-test.html |title=Browser Gamma-Consistency Test |last=Roelofs |first=Greg |website=www.libpng.org |date=2005-08-21 |access-date=2020-01-25}}</ref> This situation has since improved, as most major browsers now support the gamma setting (or lack of it).<ref>{{Cite web |title=Gamma Test Page: Gamma-labelled PNGs (1/1.6) on HTML Colors |url=http://www.libpng.org/pub/png/colorcube/colorcube-pngs-gamma16.html |access-date=2023-07-26 |website=www.libpng.org}}</ref><ref>{{cite web|url=https://pmt.sourceforge.io/gamma_test/|title=Browser gamma test}}</ref>