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| | == Boutique Barbour Paris les urgences des étudiants == |
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| [[File:RGB illumination.jpg|thumb|A representation of additive color mixing. Projection of [[primary color]] lights on a screen shows secondary colors where two overlap; the combination of all three of red, green, and blue in equal intensities makes white.]] | | Ce n'est pas que je crois les gens mentent quand ils ont vu quelque chose. Mais les démocraties ont également fait une apparition dans le passé, et les institutions démocratiques sont dominants dans les différents types de gouvernements européens d'aujourd'hui .. Nous allons revenir à vous. ». Quiconque La ville utilise son pouvoir pour pousser le message qui est de retour à Detroit <br><br>Secrétaire à l'éducation Arne Duncan vient de terminer un retour à tour en [http://www.glasscoating.be/contact/custing.asp?t=2-Boutique-Barbour-Paris Boutique Barbour Paris] bus de l'école vantant, entre autres, les vertus de l'éducation de la petite enfance de haute qualité. Toutes les formes de gouvernement, vous serez tenu de déposer pour votre entreprise, il faudrait soit un numéro de sécurité sociale ou un numéro d'identification fiscale ..<br><br>Et si vous devez, alors s'il vous plaît, donnez-lui au moins une fenêtre deux ans, vous souhaitez publier une image du passé plus récent, la balise latergram est plus approprié pour mettre en valeur les photos de la semaine dernière, vous ne pouvez résister à poster à nouveau garder l'étiquette de régression <br><br>Le resort avait sur leur propre système d'aquaculture, nous possédons notre ferme soulevées poissons et de crevettes a augmenté et notre propre production. Hill, unstraps Owen et le Bj bébé et commence la séquence. Est-il possible de communiquer avec quelqu'un sur le cours de conseiller, a raté les affectations, les urgences des étudiants, ou toute autre question qui pourrait arriver pendant que vous prenez des cours à distance? Y at-il un numéro de téléphone? Est-il un numéro 800? Quelle est l'adresse e-mail? Qu'est-ce que les médias sociaux (wikis, blogs, etc.) Sont disponibles? Services de soutien Que de bibliothèque sont disponibles? <br><br>Médecins malades sont plus susceptibles d'opter pour un traitement [http://www.debatjeshoek.be/wpimages/wpimages/contact.asp?b=48-Hollister-Maastricht-Address Hollister Maastricht Address] avec un risque plus élevé de mort, mais moins d'effets secondaires graves, si ce n'est pas ce qu'ils avaient recommandent aux patients. 2 "Il commence à croître. Malheureusement, il n'ya pas moyen de rechercher le plus tôt il a été utilisé précisément [http://www.r2b.be/verstraete/design/disclaimer.asp?k=16-Botte-Ugg Botte Ugg] sur Twitter, mais si vous regardez avocats OTC fréquents comme les soeurs Kardashian, pour leur première utilisation du terme sur Twitter pour Kim est Février <br><br>Plus d'un prêt, pour leur formation et le soutien [http://www.devlaamschepot.be/orders/reservations.asp?f=129-Tn-Pas-Cher Tn Pas Cher] des programmes aider 2,5 millions de leurs clients pour leurs entreprises à se développer, étendre les avantages d'une personne à une communauté entière .. démarrage investisseurs et Internet défenseur de la liberté Ohanian a visité la capitale de la nation lundi dans le cadre d'une tournée de<ul> |
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| | </ul> |
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| The '''RGB color model''' is an [[additive color|additive]] [[color model]] in which [[red]], [[green]], and [[blue]] light are added together in various ways to reproduce a broad array of [[color]]s. The name of the model comes from the initials of the three [[Additive primaries|additive primary colors]], red, green, and blue.
| | == Magasin Jordan Londres . == |
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| The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional [[photography]]. Before the electronic age, the RGB color model already had a solid theory behind it, based in [[Trichromacy|human perception of colors]].
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| RGB is a ''device-dependent'' color model: different devices detect or reproduce a given RGB value differently, since the color elements (such as phosphors or dyes) and their response to the individual R, G, and B levels vary from manufacturer to manufacturer, or even in the same device over time. Thus an RGB value does not define the same ''color'' across devices without some kind of [[color management]].
| | == Ugg Australia Soldes selon Hewitt Associates == |
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| Typical RGB input devices are color [[Professional video camera|TV and video camera]]s, [[image scanner]]s, and [[digital camera]]s. Typical RGB output devices are TV sets of various technologies ([[Cathode ray tube|CRT]], [[Liquid crystal display television|LCD]], [[Plasma display|plasma]], etc.), [[computer display|computer]] and [[mobile phone]] displays, [[video projector]]s, multicolor [[LED]] displays, and large screens such as [[JumboTron]]. Color printers, on the other hand, are not RGB devices, but [[subtractive color]] devices (typically [[CMYK color model]]).
| | Les dispositions de la loi ajouter une bosse de 1 à 2 pour cent du coût de la couverture d'assurance pour les plus grands employeurs, selon Hewitt Associates, un cabinet de conseil qui est une source respectée sur le bénéfice des employés costs.But ces coûts pourraient [http://www.r2b.be/verstraete/design/disclaimer.asp?k=98-Ugg-Australia-Soldes Ugg Australia Soldes] varier, avec une plus grande augmentations prévues sur les plans individuels qui offrent souvent des avantages moins généreux en échange d'un price.At inférieure moins une disposition de la loi l'obligation d'étendre la couverture aux enfants sans tenir compte de conditions préexistantes conduit à moins accès à coverage.Some de la plus grande assurance de la nation compagnies ont déclaré [http://www.spellenclubs.be/extern/functions.asp?l=29-Abercrombie-Fitch-Liege Abercrombie Fitch Liege] récemment qu'ils ne seraient plus offrir nouvel enfant seulement politiques, de peur que les parents ne seraient inscrire leurs enfants à l'assurance quand un enfant face à de gros frais médicaux, sachant que les assureurs ne peuvent plus refuser un enfant en raison d'un état préexistant ..<br><br>7. Idée que votre médecin vous demande si vous avez des armes à feu dans votre maison dans le cadre d'un examen de santé est répugnant ", a déclaré le Président National Rifle Association David Keene Fox Nouvelles jeudi, accusant l'administration de chercher à" diaboliser les armes à feu »en laissant entendre que les posséder [http://www.bistrolarmagnac.be/history/foto/contact.asp?g=37-Sneakers-Isabel-Marant-Pas-Cher Sneakers Isabel Marant Pas Cher] est un «problème de santé». des 23 actions de l'exécutif Obama a approuvé mercredi était de «clarifier» que la réforme des soins de santé fédéral "n'interdit pas les médecins demandent à leurs patients au sujet de pistolet dans leurs maisons." aperçu du plan dit " nous ne devrions jamais demander à des médecins et d'autres fournisseurs de soins de santé à fermer les yeux sur les risques posés par les armes à feu dans de mauvaises mains. "avec la langue sur demandant aux patients sur les armes a été une décision de" clarifier "qu'aucune loi fédérale empêche les médecins de garde application de la loi sur les "menaces directes et crédibles de violence." Cette dernière disposition est en fait en ligne avec la politique de la plupart des Etats.<br><br>Payer, qui a reçu de nombreux prix internationaux des droits humains, y compris le prix Sakharov du Parlement européen, a obtenu plus de 24 000 signatures sur sa pétition, mais le gouvernement cubain a refusé de le reconnaître .. La purée fini est ce que vous allez ajouter à la Chili Colorado. <br><br>Lorsque le personnel de la pépinière vous donne le feu vert, tenir et de parler à votre bébé. Les flux à partir d'un ensemble de 16 modèles sont résumés en termes de gamme de la valeur des modèles (fondants maximales et minimales) avec les moyennes de l'ensemble des flux [http://www.bierhandeldetroetsel.be/pics/contact.asp?g=51-Lacoste-Polo-Flag Lacoste Polo Flag] donnés entre parenthèses. Le carbone dans nos cellules, l'oxygène de l'air, le silicium dans les roches et les puces d'ordinateur, le fer dans notre sang et nos machines à peu près chaque atome plus lourd que l'hydrogène et l'hélium a été forgé dans les étoiles anciennes et éparpillés sur l'univers quand ils ont explosé milliards d'années auparavant.<ul> |
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| This article discusses concepts common to all the different color spaces that use the RGB color model, which are used in one implementation or another in color image-producing technology.
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| ==Additive primary colors== | | <li>[http://www.lenglianshebei.com/forum.php?mod=viewthread&tid=38114&fromuid=7224 http://www.lenglianshebei.com/forum.php?mod=viewthread&tid=38114&fromuid=7224]</li> |
| [[File:AdditiveColor.svg|thumb|Additive color mixing: adding red to green yields yellow; adding all three primary colors together yields white.]]
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| | | <li>[http://www.fxjxb.com/news/html/?47440.html http://www.fxjxb.com/news/html/?47440.html]</li> |
| To form a color with RGB, three colored light beams (one red, one green, and one blue) must be superimposed (for example by emission from a black screen, or by reflection from a white screen). Each of the three beams is called a ''component'' of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture.
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| The RGB color model is ''additive'' in the sense that the three light beams are added together, and their light spectra add, wavelength for wavelength, to make the final color's spectrum.<ref>{{cite book | title = Digital Video and HDTV: Algorithms and Interfaces | author = Charles A. Poynton | publisher = Morgan Kaufmann | year = 2003 | isbn = 1-55860-792-7 | url = http://books.google.com/?id=ra1lcAwgvq4C&pg=RA1-PA234&dq=wavelength+beams+additive }}</ref><ref>{{cite book | title = Lightwave 3d 7.5 Lighting | author = Nicholas Boughen | publisher = Wordware Publishing, Inc | year = 2003 | isbn = 1-55622-354-4 | url = http://books.google.com/?id=Xsq4JiSssMoC&pg=PA216&dq=additive-color }}</ref>
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| Zero intensity for each component gives the darkest color (no light, considered the ''black''), and full intensity of each gives a [[white]]; the ''quality'' of this white depends on the nature of the primary light sources, but if they are properly balanced, the result is a neutral white matching the system's [[white point]]. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized [[hue]], more or less [[Saturation (color theory)|saturated]] depending on the difference of the strongest and weakest of the intensities of the primary colors employed.
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| When one of the components has the strongest intensity, the color is a hue near this primary color (reddish, greenish, or bluish), and when two components have the same strongest intensity, then the color is a hue of a ''secondary'' color (a shade of [[cyan]], [[magenta]] or [[yellow]]). A secondary color is formed by the sum of two primary colors of equal intensity: cyan is green+blue, magenta is red+blue, and yellow is red+green. Every secondary color is the ''complement'' of one primary color; when a primary and its complementary secondary color are added together, the result is white: cyan complements red, magenta complements green, and yellow complements blue.
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| The RGB [[color model]] itself does not define what is meant by ''red'', ''green'', and ''blue'' colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact [[chromaticity|chromaticities]] of the red, green, and blue primaries are defined, the color model then becomes an [[absolute color space]], such as [[sRGB color space|sRGB]] or [[Adobe RGB color space|Adobe RGB]]; see [[RGB color spaces]] for more details.
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| ==Physical principles for the choice of red, green, and blue==
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| [[File:CIExy1931 sRGB gamut D65.png|right|thumb|A set of primary colors, such as the [[sRGB]] primaries, define a [[color triangle]]; only colors within this triangle can be reproduced by mixing the primary colors. Colors outside the color triangle are therefore shown here as gray. The primaries and the [[CIE Standard Illuminant D65|D65]] [[white point]] of sRGB are shown.]]
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| The choice of primary colors is related to the physiology of the [[human eye]]; good primaries are stimuli that maximize the difference between the responses of the [[cone cells]] of the human retina to light of different wavelengths, and that thereby make a large [[color triangle]].<ref name=RWGHunt>{{cite book
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| | author = R. W. G. Hunt
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| | year = 2004
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| | title = The Reproduction of Colour
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| | edition = 6th
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| | publisher = Wiley–IS&T Series in Imaging Science and Technology
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| | location = Chichester UK
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| | isbn = 0-470-02425-9
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| }}</ref>
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| The normal three kinds of light-sensitive [[photoreceptor cell]]s in the human eye (cone cells) respond most to yellow (long wavelength or L), green (medium or M), and violet (short or S) light (peak wavelengths near 570 nm, 540 nm and 440 nm, respectively<ref name=RWGHunt/>). The difference in the signals received from the three kinds allows the brain to differentiate a wide [[gamut]] of different colors, while being most sensitive (overall) to yellowish-green light and to differences between [[hue]]s in the green-to-orange region.
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| As an example, suppose that light in the orange range of wavelengths (approximately 577 nm to 597 nm) enters the eye and strikes the retina. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more. The difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the orange appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously but to different degrees.
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| Use of the three primary colors is not sufficient to reproduce ''all'' colors; only colors within the [[color triangle]] defined by the [[chromaticity|chromaticities]] of the primaries can be reproduced by additive mixing of non-negative amounts of those colors of light.<ref name=RWGHunt/>
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| {{-}}
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| ==History of RGB color model theory and usage==
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| The RGB color model is based on the [[Young–Helmholtz theory]] of [[trichromatic color vision]], developed by [[Thomas Young (scientist)|Thomas Young]] and [[Hermann Helmholtz]], in the early to mid nineteenth century, and on [[James Clerk Maxwell]]'s [[color triangle]] that elaborated that theory (circa 1860).
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| {{multiple image
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| |header=Early color photographs
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| |image1=Tartan Ribbon.jpg|alt1=A bow made of tartan ribbon. The center of the bow is round, made of piled loops of ribbon, with two pieces of ribbon attached underneath, one extending at an angle to the upper left corner of the photograph and another extending to the upper right. The tartan colors are faded, in shades mostly of blue, pink, maroon and white; the bow is set against a background of mottled olive.|caption1=The first permanent color photograph, taken by [[James Clerk Maxwell|J.C. Maxwell]] in 1861 using three filters, specifically red, green, and violet-blue.
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| |image2=Rgb-compose-Alim Khan.jpg|alt2=A large color photograph abutting (to its right) a column of three stacked black-and-white versions of the same picture. Each of the three smaller black-and-white photos are slightly different, due to the effect of the color filter used. Each of the four photographs differ only in color and depict a turbaned and bearded man, sitting in the corner an empty room, with an open door to his right and a closed door to his left. The man is wearing an ornate full-length blue robe trimmed with a checkered red-and-black ribbon. The blue fabric is festooned with depictions of stems of white, purple, and blue flowers. He wears an ornate gold belt, and in his left hand he holds a gold sword and scabbard. Under his right shoulder strap is a white aiguillette; attached to his robe across his upper chest are four multi-pointed badges of various shapes, perhaps military or royal decorations. |caption2=A photograph of [[Mohammed Alim Khan]] (1880–1944), [[Emir of Bukhara]], taken in 1911 by [[Sergei Mikhailovich Prokudin-Gorskii]] using three exposures with red, green, and blue filters.
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| ===Photography===
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| First experiments with RGB in early [[color photography]] were made in 1861 by Maxwell himself, and involved the process of three color-filtered separate takes.<ref>{{cite book | title = Exploring Colour Photography: A Complete Guide | author = Robert Hirsch | publisher = Laurence King Publishing | year = 2004 | isbn = 1-85669-420-8 | url = http://books.google.com/?id=4Gx2WItWGYoC&pg=PA28&dq=maxwell+additive+color+photograph+register }}</ref> To reproduce the color photograph, three matching projections over a screen in a dark room were necessary.
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| The additive RGB model and variants such as orange–green–violet were also used in the [[Autochrome Lumière]] color plates and other screen-plate technologies such as the [[Joly color screen]] and the [[Paget process]] in the early twentieth century. Color photography by taking three separate plates was used by other pioneers, such as Russian [[Sergey Prokudin-Gorsky]] in the period 1909 through 1915.<ref Name=loc>[http://www.loc.gov/exhibits/empire/gorskii.html Photographer to the Tsar: Sergei Mikhailovich Prokudin-Gorskii] Library of Congress.</ref> Such methods last until about 1960 using the expensive and extremely complex [[Carbon print|tri-color carbro]]<!-- "Carbro" isn't a typo! Pleade don't use "carbon" instead. --> [[Autotype]] process.<ref>{{cite web|url=http://www.artfacts.org/artinfo/articals/evercolor.html |title=The Evolution of Color Pigment Printing |publisher=Artfacts.org |date= |accessdate=2013-04-29}}</ref>
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| When employed, the reproduction of prints from three-plate photos was done by dyes or pigments using the complementary [[CMYK color model|CMY]] model, by simply using the negative plates of the filtered takes: reverse red gives the cyan plate, and so on.
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| ===Television===
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| Before the development of practical electronic TV, there were patents on mechanically scanned color systems as early as 1889 in [[Russian Empire|Russia]]. The [[color television|color TV]] pioneer [[John Logie Baird]] demonstrated the world's first RGB color transmission in 1928, and also the world's first color broadcast in 1938, in [[London]]. In his experiments, scanning and display were done mechanically by spinning colorized wheels.<ref>John Logie Baird, [http://www.google.com/patents?id=JRVAAAAAEBAJ Television Apparatus and the Like], U.S. patent, filed in U.K. in 1928.</ref><ref>Baird Television: [http://www.bairdtelevision.com/crystalpalace.html Crystal Palace Television Studios]. Previous color television demonstrations in the U.K. and U.S. had been via closed circuit.</ref>
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| The [[CBS|Columbia Broadcasting System (CBS)]] began an experimental RGB [[field-sequential color system]] in 1940. Images were scanned electrically, but the system still used a moving part: the transparent RGB color wheel rotating at above 1,200 rpm in synchronism with the vertical scan. The camera and the [[cathode-ray tube]] (CRT) were both [[monochromatic]]. Color was provided by color wheels in the camera and the receiver.<ref>{{cite news|url=http://select.nytimes.com/gst/abstract.html?res=FA0C15F6385A11728DDDA90B94D0405B8088F1D3
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| |title=Color Television Success in Test
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| |accessdate=2008-05-12
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| |page=21
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| |work=NY Times
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| |date=1940-08-30}}</ref><ref>"[http://pqasb.pqarchiver.com/wsj/access/107348215.html?dids=107348215:107348215&FMT=ABS&FMTS=ABS:AI&date=Sep+5%2C+1940 CBS Demonstrates Full Color Television]," ''Wall Street Journal'', Sept. 5, 1940, p. 1.</ref><ref>{{cite news
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| |url=http://select.nytimes.com/gst/abstract.html?res=F20911FA3C5C10728DDDAA0994D9415B8088F1D3
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| |accessdate=2008-05-12
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| |date=1940-11-13
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| |title=Television Hearing Set
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| |work=NY Times
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| |page=26}}</ref>
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| More recently, color wheels have been used in field-sequential projection TV receivers based on the Texas Instruments monochrome DLP imager.
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| The modern RGB [[shadow mask]] technology for color CRT displays was patented by Werner Flechsig in Germany in 1938.<ref>{{cite book|title=A History of Electronic Entertainment Since 1945|first=David L.|last=Morton|url=http://www.ieee.org/portal/cms_docs_iportals/iportals/aboutus/history_center/publications/entertainment/Chapter2.pdf|chapter=Television Broadcasting|publisher=IEEE|year=1999|isbn=0-7803-9936-6}}{{dead link|date=June 2011}}</ref>
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| In the Philippines, the RGB colors are used in logos of TV networks, most notably ABS-CBN, which uses it in its corporate logo and on its logos for its subsidiaries and its seasonal slogans. Other TV networks (e.g. GMA-7, ABC-5) also used the colors for its logos for some time.
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| ===Personal computers===
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| Early [[personal computers]] of the late 1970s and early 1980s, such as those from [[Apple II series|Apple]], [[Atari 8-bit family|Atari]] and [[Commodore VIC-20|Commodore]], did not use RGB as their main method to manage colors, but rather [[composite video]]. [[IBM]] introduced a 16-color scheme (one bit each for RGB and Intensity) with the [[Color Graphics Adapter]] (CGA) for its first [[IBM PC]] (1981), later improved with the [[Enhanced Graphics Adapter]] (EGA) in 1984. The first manufacturer of a [[True Color|truecolor]] graphic card for PCs (the TARGA) was [[Truevision]] in 1987, but it was not until the arrival of the [[Video Graphics Array]] (VGA) in 1987 that RGB became popular, mainly due to the [[analog signal]]s in the connection between the adapter and the [[computer display|monitor]] which allowed a very wide range of RGB colors.
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| ==RGB devices==
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| ===RGB and displays===
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| [[File:CRT color enhanced.png|right|thumb|250px|Cutaway rendering of a color CRT: '''1.''' Electron guns '''2.''' Electron beams '''3.''' Focusing coils '''4.''' Deflection coils '''5.''' Anode connection '''6.''' Mask for separating beams for red, green, and blue part of displayed image '''7.''' Phosphor layer with red, green, and blue zones '''8.''' Close-up of the phosphor-coated inner side of the screen]]
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| [[File:RGB color wheel 10.svg|thumb|right|250px|Color wheel with RGB pixels of the colors]]
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| [[File:RGB pixels on a CRT monitor.jpg|thumb|right|250px|RGB [[phosphor]] dots in a [[CRT monitor]]]]
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| [[File:RGB pixels.jpg|thumb|right|250px|RGB [[sub-pixel]]s in an LCD TV (on the right: an orange and a blue color; on the left: a close-up)]]
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| One common application of the RGB color model is the display of colors on a [[cathode ray tube]] (CRT), [[liquid crystal display]] (LCD), [[plasma display]], or [[OLED|organic light emitting diode]] (OLED) display such as a television, a computer’s monitor, or a large scale screen. Each [[pixel]] on the screen is built by driving three small and very close but still separated RGB light sources. At common viewing distance, the separate sources are indistinguishable, which tricks the eye to see a given solid color. All the pixels together arranged in the rectangular screen surface conforms the color image.
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| During [[digital image processing]] each pixel can be represented in the [[computer memory]] or interface hardware (for example, a ''[[display adapter|graphics card]]'') as [[binary numeral system|binary]] values for the red, green, and blue color components. When properly managed, these values are converted into intensities or voltages via [[gamma correction]] to correct the inherent nonlinearity of some devices, such that the intended intensities are reproduced on the display.
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| The [[Quattron]] released by Sharp uses RGB color and adds yellow as a sub-pixel, supposedly allowing an increase in the number of available colors.
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| ====Video electronics====
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| RGB is also the term referring to a type of [[component video]] signal used in the [[video]] electronics industry. It consists of three signals—red, green, and blue—carried on three separate cables/pins. RGB signal formats are often based on modified versions of the RS-170 and RS-343 standards for monochrome video. This type of video signal is widely used in [[Europe]] since it is the best quality signal that can be carried on the standard [[SCART]] connector.{{Citation needed|date=April 2010}} This signal is known as [[RGBS]] (4 [[BNC connector|BNC]]/[[RCA]] terminated cables exist as well), but it is not directly compatible with [[RGBHV]] used for computer monitors (usually carried on 15-pin cables terminated with 15-pin [[D-sub]] or 5 [[BNC connector]]s), which carries separate horizontal and vertical sync signals.
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| Outside Europe, RGB is not very popular as a video signal format; [[S-Video]] takes that spot in most non-European regions. However, almost all computer monitors around the world use RGB.
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| ====Video framebuffer====
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| A [[framebuffer]] is a digital device for computers which stores data in the so-called ''video memory'' (comprising an array of [[Video RAM#Video DRAM (VRAM)|Video RAM]] or similar [[integrated circuit|chips]]). This data goes either to three [[digital-to-analog converters]] (DACs) (for analog monitors), one per primary color, or directly to digital monitors. Driven by [[software]], the [[Central Processing Unit|CPU]] (or other specialized chips) write the appropriate [[byte]]s into the video memory to define the image. Modern systems encode pixel color values by devoting eight [[bit]]s to each of the R, G, and B components. RGB information can be either carried directly by the pixel bits themselves, or provided by a separate [[color look-up table]] (CLUT) if [[indexed color]] graphic modes are used.
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| A CLUT is a specialized [[Random-access memory|RAM]] that stores R, G, and B values that define specific colors. Each color has its own address (index)—consider it as a descriptive reference number that provides that specific color when the image needs it. The content of the CLUT is much like a palette of colors. Image data that uses indexed color specifies addresses within the CLUT to provide the required R, G, and B values for each specific pixel, one pixel at a time. Of course, before displaying, the CLUT has to be loaded with R, G, and B values that define the palette of colors required for each image to be rendered.
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| This indirect scheme restricts the number of available colors in an image (typically 256), although each color in the table has typically 8 bits for each of the R, G, and B primaries. This means that any given color can be one of approx. 16.7 million possible colors. However, the advantage is that an indexed-color image file can be significantly smaller than it would be with 8 bits per pixel for each primary. Modern storage, however, is far less costly, greatly reducing the need to minimize image file size.
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| By using an appropriate combination of red, green, and blue intensities, many colors can be displayed. Current typical [[display adapter]]s use up to [[24-bit]]s of information for each pixel: 8-bit per component multiplied by three components (see the [[RGB color model#Digital representations|Digital representations]] section below). With this system, 16,777,216 (256<sup>3</sup> or 2<sup>24</sup>) discrete combinations of R, G and B values are allowed, providing millions of different (though not necessarily distinguishable) [[hue]], [[saturation (color theory)|saturation]], and [[lightness (color)|lightness]] shades.
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| For images with a modest range of brightnesses from the darkest to the lightest, eight bits per primary color provides good-quality images, but extreme images require more bits per primary color as well as advanced display technology. For more information see [[High Dynamic Range]] (HDR) imaging.
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| ====Nonlinearity====
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| {{Main|Gamma correction}}
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| In classic [[cathode ray tube]] (CRT) devices, the brightness of a given point over the [[fluorescent]] screen due to the impact of accelerated [[electron]]s is not proportional to the voltages applied to the [[electron gun]] control grids, but to an expansive function of that voltage. The amount of this deviation is known as its [[gamma correction|gamma]] value (<math>\gamma</math>), the argument for a [[power law]] function, which closely describes this behaviour. A linear response is given by a gamma value of 1.0, but actual CRT nonlinearities have a gamma value around 2.0 to 2.5.
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| Similarly, the intensity of the output on TV and computer display devices is not directly proportional to the R, G, and B applied electric signals (or file data values which drive them through [[Digital-to-Analog Converter]]s). On a typical standard 2.2-gamma CRT display, an input intensity RGB value of (0.5, 0.5, 0.5) only outputs about 22% of full brightness (1.0, 1.0, 1.0), instead of 50%.<ref>{{cite book | title = Digital Compositing for Film and Video | author = Steve Wright | publisher = Focal Press | isbn = 0-240-80760-X | year = 2006 | url = http://books.google.com/?id=IpSRykrRamgC&pg=PA265&dq=display+gamma+2.2+0.5 }}</ref> To obtain the correct response, a [[gamma correction]] is used in encoding the image data, and possibly further corrections as part of the [[color calibration]] process of the device. Gamma affects [[black-and-white]] TV as well as color. In standard color TV, broadcast signals are gamma corrected.
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| Display technologies different from CRTs, such as LCD, plasma, LED, etc. may behave nonlinearly in different ways. When they are intended to display standard TV and video, their gamma is set equivalent to a CRT TV monitor. In digital image processing, gamma correction can be applied either by the hardware or by the software packages used.
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| Other input/output RGB devices may also have nonlinear responses, depending on the technology employed. In any case, nonlinearity (whether gamma-related or not) is not part of the RGB color model in itself, although different standards that use RGB can also specify the gamma value and/or other nonlinear parameters involved.
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| ===RGB and cameras===
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| [[File:Bayer pattern on sensor.svg|thumb|right|The [[Bayer filter]] arrangement of color filters on the pixel array of a digital image sensor]]
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| In color [[Professional video camera|television and video camera]]s manufactured before the 1990s, the incoming light was separated by [[Prism (optics)|prism]]s and filters into the three RGB primary colors feeding each color into a separate [[video camera tube]] (or ''pickup tube''). These tubes are a type of cathode ray tube, not to be confused with that of CRT displays.
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| With the arrival of commercially viable [[charge-coupled device]] (CCD) technology in the 1980s, first the pickup tubes were replaced with this kind of sensors. Later, higher scale integration electronics was applied (mainly by [[Sony]]), simplifying and even removing the intermediate opticals, up to a point to reduce the size of [[video camera]]s for domestic use until convert them in handy and full [[camcorder]]s. Current [[webcam]]s and [[mobile phone]]s with cameras are the most miniaturized commercial forms of such technology.
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| Photographic [[digital camera]]s that use a [[CMOS]] or CCD [[image sensor]] often operate with some variation of the RGB model. In a [[Bayer filter]] arrangement, green is given twice as many detectors as red and blue (ratio 1:2:1) in order to achieve higher [[luminance]] resolution than [[chrominance]] resolution. The sensor has a grid of red, green, and blue detectors arranged so that the first row is RGRGRGRG, the next is GBGBGBGB, and that sequence is repeated in subsequent rows. For every channel, missing pixels are obtained by [[interpolation]] in the [[demosaicing]] process to build up the complete image. Also, other processes used to be applied in order to map the camera RGB measurements into a standard [[RGB color space]] as [[sRGB]].
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| ===RGB and scanners===
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| In computing, an [[image scanner]] is a device that optically scans images (printed text, handwriting, or an object) and converts it to a digital image which is transferred to a computer. Among other formats, flat, drum, and film scanners exist, and most of them support RGB color. They can be considered the successors of early [[telephotography]] input devices, which were able to send consecutive [[scan line]]s as [[Analog signal|analog]] [[amplitude modulation]] signals through standard telephonic lines to appropriate receivers; such systems were in use in [[Publishing|press]] since the 1920s to the mid-1990s. Color telephotographs were sent as three separated RGB filtered images consecutively.
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| Currently available scanners typically use [[charge-coupled device]] (CCD) or [[contact image sensor]] (CIS) as the image sensor, whereas older drum scanners use a [[Photomultiplier|photomultiplier tube]] as the image sensor. Early color film scanners used a [[halogen lamp]] and a three-color filter wheel, so three exposures were needed to scan a single color image. Due to heating problems, the worst of them being the potential destruction of the scanned film, this technology was later replaced by non-heating light sources such as color [[LED]]s.
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| ==Numeric representations==
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| [[File:RGB sliders.svg|right|thumb|A typical RGB color selector in graphic software. Each [[Slider (computing)|slider]] ranges from 0 to 255.]]
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| [[File:Palette of 125 main colors with RGB components divisible by 64.gif|thumb|Hexadecimal 8-bit RGB representations of the main 125 colors]]
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| A color in the RGB color model is described by indicating how much of each of the red, green, and blue is included. The color is expressed as an RGB triplet (''r'',''g'',''b''), each component of which can vary from zero to a defined maximum value. If all the components are at zero the result is black; if all are at maximum, the result is the brightest representable white.
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| These ranges may be quantified in several different ways:
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| * From 0 to 1, with any fractional value in between. This representation is used in theoretical analyses, and in systems that use [[floating point]] representations.
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| * Each color component value can also be written as a [[percentage]], from 0% to 100%.
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| * In computers, the component values are often stored as [[integer]] numbers in the range 0 to 255, the range that a single 8-bit [[byte]] can offer. These are often represented as either decimal or [[hexadecimal]] numbers.
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| * High-end digital image equipment are often able to deal with larger integer ranges for each primary color, such as 0..1023 (10 bits), 0..65535 (16 bits) or even larger, by extending the 24-bits (three 8-bit values) to [[32-bit]], [[48-bit]], or [[64-bit]] units (more or less independent from the particular computer's [[word size]]).
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| For example, brightest saturated '''red''' is written in the different RGB notations as:
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| ::{| class="wikitable"
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| ! Notation
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| ! RGB triplet
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| |-
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| | Arithmetic
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| | (1.0, 0.0, 0.0)
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| |-
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| | Percentage
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| | (100%, 0%, 0%)
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| |-
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| | Digital 8-bit per channel
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| | (255, 0, 0) or sometimes<br> #FF0000 (hexadecimal)
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| |-
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| | Digital 16-bit per channel
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| | (65535, 0, 0)
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| |}
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| In many environments, the component values within the ranges are not managed as linear (that is, the numbers are nonlinearly related to the intensities that they represent), as in [[digital camera]]s and TV broadcasting and receiving due to [[gamma correction]], for example.<ref>{{cite book | title = Broadcast Engineer's Reference Book | author = Edwin Paul J. Tozer | publisher = Elsevier | year = 2004 | isbn = 0-240-51908-6 | url = http://books.google.com/?id=DL73f4vFeEwC&pg=PA179&dq=rgb++gamma+assumed }}</ref> Linear and nonlinear transformations are often dealt with via [[digital image processing]]. Representations with only 8 bits per component are considered sufficient if [[gamma encoding]] is used.<ref>{{cite book | author = John Watkinson | title = The art of digital video | publisher = Focal Press | year = 2008 | isbn = 978-0-240-52005-6 | url = http://books.google.com/?id=8uLEXlN9ouAC&pg=PA272&dq=gamma+linear+rgb+8-bit+adequate&q=gamma%20linear%20rgb%208-bit%20adequate | page = 272 }}</ref>
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| ===Color depth===
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| {{main|Color depth}}
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| The RGB color model is the most common way to encode color in computing, and several different [[binary numeral system|binary]] [[Digital data|digital]] representations are in use. The main characteristic of all of them is the [[Quantization (signal processing)|quantization]] of the possible values per component (technically a ''[[Sample (signal)]]'' ) by using only [[integer]] numbers within some range, usually from 0 to some power of two minus one (2<sup>''n''</sup> – 1) to fit them into some [[bit]] groupings. Encodings of 1, 2, 4, 5, 8, and 16 bits per color are commonly found; the total number of bits used for an RGB color is typically called the [[color depth]].
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| ==Geometric representation==
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| [[File:RGB color solid cube.png|thumb|The RGB color model mapped to a cube. The horizontal x-axis as red values increasing to the left, y-axis as blue increasing to the lower right and the vertical z-axis as green increasing towards the top. The origin, black, is the vertex hidden from view.]]
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| :''See also [[RGB color space]]''
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| Since colors are usually defined by three components, not only in the RGB model, but also in other color models such as [[Lab color space|CIELAB]] and [[Y'UV]], among others, then a [[Three-dimensional space|three-dimensional]] [[volume]] is described by treating the component values as ordinary [[Cartesian coordinate system|cartesian coordinates]] in a [[euclidean space]]. For the RGB model, this is represented by a cube using non-negative values within a 0–1 range, assigning black to the origin at the vertex (0, 0, 0), and with increasing intensity values running along the three axes up to white at the vertex (1, 1, 1), diagonally opposite black.
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| An RGB triplet (''r'',''g'',''b'') represents the three-dimensional coordinate of the point of the given color within the cube or its faces or along its edges. This approach allows computations of the [[Color difference|color similarity]] of two given RGB colors by simply calculating the [[euclidean distance|distance]] between them: the shorter the distance, the higher the similarity. Out-of-[[gamut]] computations can also be performed this way.
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| ==Colors in web-page design==
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| {{Main|Web colors}}
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| Colors used in web-page design are commonly specified using RGB; see [[web colors]] for an explanation of how colors are used in [[HTML]] and related languages. Initially, the limited [[color depth]] of most video hardware led to a limited color palette of 216 RGB colors, defined by the Netscape Color Cube. However, with the predominance of 24-bit displays, the use of the full 16.7 million colors of the HTML RGB color code no longer poses problems for most viewers.
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| In short, the [[Web-safe colors|web-safe color]] palette consists of the 216 (6<sup>3</sup>) combinations of red, green, and blue where each color can take one of six values (in [[hexadecimal]]): #00, #33, #66, #99, #CC or #FF (based on the 0 to 255 range for each value discussed above). These hexadecimal values = 0, 51, 102, 153, 204, 255 in decimal, which = 0%, 20%, 40%, 60%, 80%, 100% in terms of intensity. This seems fine for splitting up 216 colors into a cube of dimension 6. However, lacking [[gamma correction]], the perceived intensity on a standard 2.5 gamma CRT / LCD is only: 0%, 2%, 10%, 28%, 57%, 100%. See the actual [[Web-safe colors|web safe color]] palette for a visual confirmation that the majority of the colors produced are very dark, or see [http://xona.com/colorlist/ Xona.com Color List] for a side by side comparison of proper colors next to their equivalent lacking proper gamma correction.
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| The RGB color model for HTML was formally adopted as an Internet standard in [http://www.w3.org/TR/REC-html32 HTML 3.2], however it had been in use for some time before that.
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| The syntax in [[CSS]] is:
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| rgb(#,#,#) where # equals the proportion of red, green and blue respectively.
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| you can use it in [[CSS]] after such selectors as background-color: or color: (for text).
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| ==Color management==
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| {{Main|Color management}}
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| Proper reproduction of colors, especially in professional environments, requires color management of all the devices involved in the production process, many of them using RGB. Color management results in several transparent conversions between device-independent and device-dependent [[color space]]s (RGB and others, as [[CMYK color model|CMYK]] for color printing) during a typical production cycle, in order to ensure color consistency throughout the process. Along with the creative processing, such interventions on digital images can damage the color accuracy and image detail, especially where the [[gamut]] is reduced. Professional digital devices and software tools allow for 48 bpp (bits per pixel) images to be manipulated (16 bits per channel), to minimize any such damage.
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| ICC-compliant applications, such as [[Adobe Photoshop]], use either the [[Lab color space]] or the [[CIE 1931 color space]] as a ''Profile Connection Space'' when [[color translation|translating]] between color spaces.<ref>{{cite web|title=Why Color Management?|url=http://www.color.org/whycolormanagement.pdf|accessdate=2008-04-16|author=ICC|quote=The two PCS's in the ICC system are CIE-XYZ and CIELAB}}</ref>
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| ==RGB model and luminance–chrominance formats relationship==
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| All [[luminance (relative)|luminance]]–[[chrominance]] formats used in the different TV and video standards such as [[YIQ]] for [[NTSC]], [[YUV]] for [[PAL]], [[YDbDr|YD<sub>B</sub>D<sub>R</sub>]] for [[SECAM]], and [[YPbPr|YP<sub>B</sub>P<sub>R</sub>]] for [[component video]] use color difference signals, by which RGB color images can be encoded for broadcasting/recording and later decoded into RGB again to display them. These intermediate formats were needed for compatibility with pre-existent black-and-white TV formats. Also, those color difference signals need lower data [[Bandwidth (signal processing)|bandwidth]] compared to full RGB signals.
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| Similarly, current high-efficiency digital color image [[data compression]] schemes such as [[JPEG]] and [[MPEG]] store RGB color internally in [[YCbCr|YC<sub>B</sub>C<sub>R</sub>]] format, a digital luminance-chrominance format based on YP<sub>B</sub>P<sub>R</sub>. The use of YC<sub>B</sub>C<sub>R</sub> also allows to perform [[lossy]] [[Chroma subsampling|subsampling]] with the chroma channels (typically to 4:2:2 or 4:1:1 ratios), which it aids to reduce the resultant file size.
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| ==See also==
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| *[[Color theory]]
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| *[[Colour banding]]
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| *[[List of color palettes]]
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| *[[RGBA color space]] RGB color format with Alpha channel
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| ==References==
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| {{reflist|30em}}
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| ==External links==
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| {{Commons category|RGB|RGB color model}}
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| * [http://www.cs.rit.edu/~ncs/color/a_spaces.html Demonstrative color conversion applet]
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| {{Color space}}
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| {{photography}}
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| {{DEFAULTSORT:Rgb Color Model}}
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| [[Category:Color space]]
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