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| {{lowercase|title=scRGB}}
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| [[File:ScRGB.svg|right|thumb|300px|Intersection of the scRGB [[gamut]] with the X+Y+Z=.6443 plane (the gamut varies depending on the intensity as it is a cube with a non-zero origin).]]
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| '''scRGB''' is a wide color [[gamut]] [[RGB color spaces|RGB (Red Green Blue) color space]] created by [[Microsoft]] and [[Hewlett-Packard|HP]] that uses the same color primaries and white/black points as the [[sRGB]] color space but allows coordinates below zero and greater than one. The full range is -0.5 through just less than +7.5.
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| Negative numbers enables scRGB to encompass most of the [[CIE 1931 color space]] while maintaining simplicity and backward compatibility with sRGB without the complexity of [[color management]]. The cost of maintaining compatibility with sRGB is that approximately 80% of the scRGB color space consists of [[imaginary color]]s.
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| Large positive numbers allow [[high dynamic range]] images to be represented, though the range is inferior to that of some other high dynamic range formats such as [[OpenEXR]].<ref>[http://www.anyhere.com/gward/hdrenc/hdr_encodings.html "High Dynamic Range Image Encodings". Greg Ward. Retrieved 2010-10-25.]</ref>
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| == Encoding ==
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| Two encodings are defined for the individual primaries: a linear 16 bit per channel encoding and a nonlinear 12 bit per channel encoding.
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| The 16 bit '''scRGB(16)''' encoding is the ''linear'' RGB channels converted by <math>8192 x + 4096</math>. Compared to 8-bit sRGB this ranges from about 1/2 the color resolution near 0.0 to more than 10 times the color resolution near 1.0. Storage as 16 bits clamps the linear range to <math>-0.5 .. 7.4999</math>.
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| The 12-bit '''scRGB-nl''' encoding is the linear RGB channels passed through the same gamma function as [[sRGB]] (for negative numbers use -f(-x)) and then converted by <math>1280 x + 1024</math>. This is exactly 5 times the color resolution of 8-bit sRGB, and 8-bit sRGB can be converted directly with <math>5 x + 1024</math>. The linear range is clamped to the slightly larger <math>-0.6038 .. 7.5913</math>
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| A 12-bit encoding called '''scYCC-nl''' is the conversion of the non-linear [[sRGB]] levels to [[yCbCr|JFIF-Y'CbCr]] and then converted by <math>1280 Y' + 1024</math> and <math>1280 Cx + 2048</math>. This form can allow greater compression and direct conversion to/from [[JPEG]] files and video hardware.
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| With the addition of an alpha channel with the same number of bits the 16-bit encoding may be seen referred to as 64 bit and the 12-bit encoding referred to as 48-bit. Alpha is not encoded as above, however. Alpha is instead a linear 0-1 range multiplied by <math>2^n-1</math> where <math>n</math> is 12 or 16.
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| == Usage ==
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| The first implementation of scRGB was the [[Graphics Device Interface#GDI+|GDI+]] API in [[Windows Vista]]. At [[Windows Hardware Engineering Conference|WinHEC]] 2008 Microsoft announced that [[Windows 7]] would support 48-bit scRGB (which for [[High-Definition Multimedia Interface|HDMI]] can be converted and output as [[xvYCC]]). The components in Windows 7 that support 48-bit scRGB are [[Direct3D]], the [[Windows Imaging Component]], and the [[Windows Color System]] and they support it in both full screen exclusive mode and in video overlays.<ref>{{cite web|url=http://download.microsoft.com/download/5/E/6/5E66B27B-988B-4F50-AF3A-C2FF1E62180F/GRA-T583_WH08.pptx |title=WinHEC 2008 GRA-583: Display Technologies |publisher=Microsoft |date=2008-11-06 |accessdate=2008-12-06}}</ref><ref>{{cite web|url=http://news.softpedia.com/news/Windows-7-High-Color-Support-98741.shtml |title=Windows 7 High Color Support |publisher=Softpedia |date=2008-11-26 |accessdate=2008-12-06}}</ref>
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| ==See also==
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| {{portal box|Color|Computer graphics}}
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| == References ==
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| <references/>
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| == External links ==
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| * [http://webstore.iec.ch/webstore/webstore.nsf/artnum/029678 The standard IEC 61966-2-2]
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| * [http://www.iec.ch/cgi-bin/getcorr.pl?file=iec61966-2-2-cor1{ed1.0}en.pdf Annex B: Non-linear encoding for scRGB : scRGB-nl]
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| * A [http://www.colour.org/tc8-05/Docs/colorspace/61966-2-2NPa.pdf working draft] of IEC 61966-2-2 is available online.
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| * [http://www.pcmag.com/article2/0,2817,13769,00.asp PCMag.com: Defining scRGB]
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| {{Color space}}
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| {{DEFAULTSORT:Scrgb}}
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| [[Category:Color space]]
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| [[Category:High dynamic range file formats]]
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