Color appearance model: Difference between revisions

Revision as of 21:17, 9 February 2016

Revision as of 05:55, 10 February 2016

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* '''[[Bezold–Brücke shift|Bezold–Brücke hue shift]]:''' The hue of monochromatic light changes with [[luminance]].

* '''[[Abney effect]]:''' The hue of monochromatic light changes with the addition of white light (which would be expected color-neutral).

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* '''Stevens effect:''' Contrast increases with luminance.

* '''Bartleson-Breneman effect:''' Image contrast (of emissive images such as images on an LCD display) increases with the luminance of surround lighting.

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===Spatial phenomena===

Spatial phenomena only affect colors at a specific ___location of an image, because the human brain interprets this ___location in a specific contextual way (e.g. as a shadow instead of gray color). These phenomena are also known as [[optical_illusionoptical illusion#Color and brightness constancies|optical illusions]]. Because of their contextuality, they are especially hard to model; color appearance models that are trying to do this are referred to as [[ICAM (Color Appearance Model)|image color appearance models (iCAM)]].

==Color appearance models==

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===IPT===

Ebner and Fairchild addressed the issue of non-constant lines of hue in their color space dubbed ''IPT''.<ref>

{{Citation

| last1 = Ebner

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| series = Proc. IS&T 6th Color Imaging Conference

| place = Scottsdale, AZ

| pages = 8-138–13.

| year = 1998

}}

</ref>. The IPT color space converts [[Illuminant_D65Illuminant D65|D65]]-adapted [[CIE 1931 color space|XYZ]] data (XD65, YD65, ZD65) to long-medium-short cone response data (LMS) using an adapted form of the Hunt-Pointer-Estevez matrix (MHPE(D65)).<ref>

{{cite web

| last = Edge

| first = Christopher

| title = US Patent 8,437,053, Gamut mapping using hue-preserving color space

| url = http://http://www.google.com/patents/US8437053

| access-date = 9 February 2016

}}

</ref>.

The IPT color appearance model excels at providing a formulation for hue where a constant hue value equals a constant perceived hue independent of the values of lightness and chroma (which is the general ideal for any color appearance model, but hard to achieve). It is therefore well-suited for [[Color management#Gamut mapping|gamut mapping]] implementations.