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67-597: The RGB color model is an additive color model in which the red , green and blue primary colors of light are added together in various ways to reproduce a broad array of colors . The name of the model comes from the initials of the three additive primary colors , red, green, and blue. 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 and colored lighting . Before

134-565: A central or neutral point or axis on a color space coordinate diagram (such as a chromaticity diagram ) or color wheel , or by its dominant wavelength or by that of its complementary color . The other color appearance parameters are colorfulness , saturation (also known as intensity or chroma), lightness , and brightness . Usually, colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness - for example: "light blue", " pastel blue", "vivid blue", and "cobalt blue". Exceptions include brown , which

201-449: A few more years because the original VGA cards were palette-driven just like EGA, although with more freedom than VGA, but because the VGA connectors were analog, later variants of VGA (made by various manufacturers under the informal name Super VGA) eventually added true-color. In 1992, magazines heavily advertised true-color Super VGA hardware. One common application of the RGB color model is

268-404: A fourth greyscale color channel as a masking layer, often called RGB32 . 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 the advanced display technology. For more information see High Dynamic Range (HDR) imaging. In classic CRT devices,

335-453: A gray or black background. Additive color models are applied in the design and testing of electronic displays that are used to render realistic images containing diverse sets of color using phosphors that emit light of a limited set of primary colors . Examination with a sufficiently powerful magnifying lens will reveal that each pixel in CRT , LCD , and most other types of color video displays

402-417: A polar plot, which he termed a color circle. Using R, G, and B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, and B prevail, then apply the formula given in the table below. In each case the formula contains the fraction M − L H − L {\displaystyle {\frac {M-L}{H-L}}} , where H

469-595: 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. Some video applications store such palettes in PAL files ( Age of Empires game, for example, uses over half-a-dozen) and can combine CLUTs on screen. This indirect scheme restricts the number of available colors in an image CLUT—typically 256-cubed (8 bits in three color channels with values of 0–255)—although each color in

536-829: Is Δ h a b {\displaystyle \Delta h_{ab}} in CIELAB and Δ h u v {\displaystyle \Delta h_{uv}} in CIELUV. The other is computed as the residual total color difference after Lightness and Chroma differences have been accounted for; its symbol is Δ H a b ∗ {\displaystyle \Delta H_{ab}^{*}} in CIELAB and Δ H u v ∗ {\displaystyle \Delta H_{uv}^{*}} in CIELUV. There exists some correspondence, more or less precise, between hue values and color terms (names). One approach in color science

603-419: Is a dark orange . In painting , a hue is a pure pigment —one without tint or shade (added white or black pigment, respectively). The human brain first processes hues in areas in the extended V4 called globs . The concept of a color system with a hue was explored as early as 1830 with Philipp Otto Runge 's color sphere. The Munsell color system from the 1930s was a great step forward, as it

670-436: Is a specialized 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

737-447: Is composed of red, green, and blue light-emitting phosphors which appear as a variety of single colors when viewed from a normal distance. Additive color, alone, does not predict the appearance of mixtures of printed color inks, dye layers in color photographs on film , or paint mixtures. Instead, subtractive color is used to model the appearance of pigments or dyes , such as those in paints and inks . The combination of two of

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804-402: Is formed by the sum of two primary colors of equal intensity: cyan is green+blue, magenta is blue+red, and yellow is red+green. Every secondary color is the complement of one primary color: cyan complements red, magenta complements green, and yellow complements blue. When all the primary colors are mixed in equal intensities, the result is white. The RGB color model itself does not define what

871-525: Is given by a gamma value of 1.0, but actual CRT nonlinearities have a gamma value around 2.0 to 2.5. 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 converters). 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%. To obtain

938-422: 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

1005-448: 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 chromaticities of the red, green, and blue primaries are defined, the color model then becomes an absolute color space , such as sRGB or Adobe RGB . The choice of primary colors is related to the physiology of the human eye ; good primaries are stimuli that maximize

1072-491: 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. A framebuffer is a digital device for computers which stores data in the so-called video memory (comprising an array of Video RAM or similar 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 ,

1139-467: Is one of the most common ways to encode color in computing, and several different digital representations are in use. The main characteristic of all of them is the quantization of the possible values per component (technically a sample ) by using only integer numbers within some range, usually from 0 to some power of two minus one (2 − 1) to fit them into some bit groupings. Encodings of 1, 2, 4, 5, 8 and 16 bits per color are commonly found;

1206-448: 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. 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

1273-459: Is the angular component of the polar representation, while chroma is the radial component. Specifically, in CIELAB while, analogously, in CIELUV where, atan2 is a two-argument inverse tangent. Preucil describes a color hexagon, similar to a trilinear plot described by Evans, Hanson, and Brewer, which may be used to compute hue from RGB . To place red at 0°, green at 120°, and blue at 240°, Equivalently, one may solve Preucil used

1340-463: Is the highest of R, G, and B; L is the lowest, and M is the mid one between the other two. This is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction. Hue angles computed for the Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° (red, yellow, green, cyan, blue, magenta, and

1407-1146: Is used. Following is the mathematical relationship between RGB space to HSI space (hue, saturation, and intensity: HSI color space ): I = R + G + B 3 S = 1 − 3 ( R + G + B ) min ( R , G , B ) H = cos − 1 ⁡ ( ( R − G ) + ( R − B ) 2 ( R − G ) 2 + ( R − B ) ( G − B ) ) assuming  G > B {\displaystyle {\begin{aligned}I&={\frac {R+G+B}{3}}\\S&=1\,-\,{\frac {3}{(R+G+B)}}\,\min(R,G,B)\\H&=\cos ^{-1}\left({\frac {(R-G)+(R-B)}{2{\sqrt {(R-G)^{2}+(R-B)(G-B)}}}}\right)\qquad {\text{assuming }}G>B\end{aligned}}} If B > G {\displaystyle B>G} , then H = 360 − H {\displaystyle H=360-H} . The RGB color model

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1474-498: Is written in the different RGB notations as: 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 cameras and TV broadcasting and receiving due to gamma correction, for example. Linear and nonlinear transformations are often dealt with via digital image processing. Representations with only 8 bits per component are considered sufficient if gamma correction

1541-449: The CPU (or other specialized chips) write the appropriate bytes into the video memory to define the image. Modern systems encode pixel color values by devoting eight bits 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. A CLUT

1608-612: The Enhanced Graphics Adapter (EGA) in 1984. The first manufacturer of a truecolor graphics 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 signals in the connection between the adapter and the monitor which allowed a very wide range of RGB colors. Actually, it had to wait

1675-582: The Jumbotron . Color printers , on the other hand, are not RGB devices, but subtractive color devices typically using the CMYK color model . To form a color with RGB, three 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

1742-494: The Numeric representations section below (24bits = 256, each primary value of 8 bits with values of 0–255). With this system, 16,777,216 (256 or 2) discrete combinations of R, G, and B values are allowed, providing millions of different (though not necessarily distinguishable) hue, saturation and lightness shades. Increased shading has been implemented in various ways, some formats such as .png and .tga files among others using

1809-410: 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,

1876-439: The color similarity of two given RGB colors by simply calculating the distance between them: the shorter the distance, the higher the similarity. Out-of-gamut computations can also be performed this way. Additive color Additive color or additive mixing is a property of a color model that predicts the appearance of colors made by coincident component lights , i.e. the perceived color can be predicted by summing

1943-403: The electronic age , the RGB color model already had a solid theory behind it, based in human perception of colors . 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 red, green, and blue levels vary from manufacturer to manufacturer, or even in

2010-458: 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. These ranges may be quantified in several different ways: For example, brightest saturated red

2077-689: The RGB24 CLUT table has only 8 bits representing 256 codes for each of the R, G, and B primaries, making 16,777,216 possible colors. However, the advantage is that an indexed-color image file can be significantly smaller than it would be with only 8 bits per pixel for each primary. Modern storage, however, is far less costly, greatly reducing the need to minimize image file size. By using an appropriate combination of red, green, and blue intensities, many colors can be displayed. Current typical display adapters use up to 24-bits of information for each pixel: 8-bit per component multiplied by three components (see

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2144-672: 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. This signal is known as RGBS (4 BNC / RCA terminated cables exist as well), but it is directly compatible with RGBHV used for computer monitors (usually carried on 15-pin cables terminated with 15-pin D-sub or 5 BNC connectors), which carries separate horizontal and vertical sync signals. Outside Europe, RGB

2211-453: The brightness of a given point over the fluorescent screen due to the impact of accelerated electrons 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 value ( γ {\displaystyle \gamma } ), the argument for a power law function, which closely describes this behavior. A linear response

2278-531: The colors midway between contiguous pairs) and differ by approximately 1.2° at odd integer multiples of 15° (based on the circle formula), the maximal divergence between the two. The process of converting an RGB color into an HSL color space or HSV color space is usually based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone , or the HSL double cone as a double hexacone. The formulae used are those in

2345-416: The common color component between them, e.g. green as the common component between yellow and cyan, red as the common component between magenta and yellow, and blue-violet as the common component between magenta and cyan. There is no color component among magenta, cyan and yellow, thus rendering a spectrum of zero intensity: black. Zero intensity for each component gives the darkest color (no light, considered

2412-426: The common three additive primary colors in equal proportions produces an additive secondary color — cyan , magenta or yellow . Additive color is also used to predict colors from overlapping projected colored lights often used in theatrical lighting for plays, concerts, circus shows, and night clubs. The full gamut of color available in any additive color system is defined by all the possible combinations of all

2479-445: The complete image. Also, other processes used to be applied in order to map the camera RGB measurements into a standard color space as sRGB. 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

2546-418: 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. In color television and video cameras manufactured before the 1990s, the incoming light was separated by prisms and filters into

2613-410: The corresponding red, green, or blue color filter used to take its image. When brought into alignment, the three images (a black-and-red image, a black-and-green image and a black-and-blue image) formed a full-color image, thus demonstrating the principles of additive color. Hue Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around

2680-682: The cyan plate, and so on. Before the development of practical electronic TV, there were patents on mechanically scanned color systems as early as 1889 in Russia . The 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. The Columbia Broadcasting System (CBS) began an experimental RGB field-sequential color system in 1940. Images were scanned electrically, but

2747-453: 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 . The normal three kinds of light-sensitive photoreceptor cells 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). The difference in

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2814-411: The display of colors on a cathode-ray tube (CRT), liquid-crystal display (LCD), plasma display , or 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

2881-462: The eye interprets as a given solid color. All the pixels together arranged in the rectangular screen surface conforms the color image. During digital image processing each pixel can be represented in the computer memory or interface hardware (for example, a graphics card ) as 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

2948-431: The image sensor, whereas older drum scanners use a 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 LEDs . A color in

3015-518: The inherent nonlinearity of some devices, such that the intended intensities are reproduced on the display. 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. 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

3082-416: The intermediate optics, thereby reducing the size of home video cameras and eventually leading to the development of full camcorders . Current webcams and mobile phones with cameras are the most miniaturized commercial forms of such technology. Photographic digital cameras that use a CMOS or CCD image sensor often operate with some variation of the RGB model. In a Bayer filter arrangement, green

3149-444: The light under which we see them. In the additive model, if the resulting spectrum, e.g. of superposing three colors, is flat, white color is perceived by the human eye upon direct incidence on the retina. This is in stark contrast to the subtractive model, where the perceived resulting spectrum is what reflecting surfaces, such as dyed surfaces, emit. A dye filters out all colors but its own; two blended dyes filter out all colors but

3216-414: 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. Use of

3283-509: The mixture. The RGB color model is additive in the sense that if light beams of differing color (frequency) are superposed in space their light spectra adds up, wavelength for wavelength, to make up a resulting, total spectrum. This is essentially opposite to the subtractive color model, particularly the CMY color model , which applies to paints, inks, dyes and other substances whose color depends on reflecting certain components (frequencies) of

3350-450: The numeric representations of the component colors. Modern formulations of Grassmann's laws describe the additivity in the color perception of light mixtures in terms of algebraic equations. Additive color predicts perception and not any sort of change in the photons of light themselves. These predictions are only applicable in the limited scope of color matching experiments where viewers match small patches of uniform color isolated against

3417-401: The original. Replacements are often used for chromium , cadmium and alizarin . Dominant wavelength (or sometimes equivalent wavelength) is a physical analog to the perceptual attribute hue. On a chromaticity diagram , a line is drawn from a white point through the coordinates of the color in question, until it intersects the spectral locus . The wavelength at which the line intersects

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3484-493: The possible luminosities of each primary color in that system. In chromaticity space, a gamut is a plane convex polygon with corners at the primaries. For three primaries, it is a triangle . Systems of additive color are motivated by the Young–Helmholtz theory of trichromatic color vision , which was articulated around 1850 by Hermann von Helmholtz , based on earlier work by Thomas Young . For his experimental work on

3551-633: The process of combining three color-filtered separate takes. To reproduce the color photograph, three matching projections over a screen in a dark room were necessary. 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

3618-469: The result is a colorized hue , more or less saturated depending on the difference of the strongest and weakest of the intensities of the primary colors employed. When one of the components has the strongest intensity, the color is a hue near this primary color (red-ish, green-ish, or blue-ish), 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

3685-471: The same device over time. Thus an RGB value does not define the same color across devices without some kind of color management . Typical RGB input devices are color TV and video cameras , image scanners , and digital cameras . Typical RGB output devices are TV sets of various technologies ( CRT , LCD , plasma , OLED , quantum dots , etc.), computer and mobile phone displays, video projectors , multicolor LED displays and large screens such as

3752-436: 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 hues in the green-to-orange region. 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

3819-409: The spectrum locus is identified as the color's dominant wavelength if the point is on the same side of the white point as the spectral locus, and as the color's complementary wavelength if the point is on the opposite side. There are two main ways in which hue difference is quantified. The first is the simple difference between the two hue angles. The symbol for this expression of hue difference

3886-401: The subject, James Clerk Maxwell is sometimes credited as being the father of additive color. He had the photographer Thomas Sutton photograph a tartan ribbon on black-and-white film three times, first with a red, then green, then blue color filter over the lens. The three black-and-white images were developed and then projected onto a screen with three different projectors, each equipped with

3953-448: The successors of early telephotography input devices, which were able to send consecutive scan lines as analog amplitude modulation signals through standard telephonic lines to appropriate receivers; such systems were in use in press since the 1920s to the mid-1990s. Color telephotographs were sent as three separated RGB filtered images consecutively. Currently available scanners typically use CCD or contact image sensor (CIS) as

4020-547: 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. More recently, color wheels have been used in field-sequential projection TV receivers based on the Texas Instruments monochrome DLP imager. The modern RGB shadow mask technology for color CRT displays

4087-459: The table above. One might notice that the HSL/HSV hue "circle" do not appear to all be of the same brightness. This is a known issue of this RGB-based derivation of hue. Manufacturers of pigments use the word hue, for example, "cadmium yellow (hue)" to indicate that the original pigmentation ingredient, often toxic, has been replaced by safer (or cheaper) alternatives whilst retaining the hue of

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4154-460: 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. With the arrival of commercially viable charge-coupled device (CCD) technology in the 1980s, first, the pickup tubes were replaced with this kind of sensor. Later, higher scale integration electronics was applied (mainly by Sony ), simplifying and even removing

4221-642: The three primary colors is not sufficient to reproduce all colors; only colors within the color triangle defined by the chromaticities of the primaries can be reproduced by additive mixing of non-negative amounts of those colors of light. The RGB color model is based on the Young–Helmholtz theory of trichromatic color vision , developed by Thomas Young and Hermann von Helmholtz in the early to mid-nineteenth century, and on James Clerk Maxwell 's color triangle that elaborated that theory ( c.  1860 ). The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, and involved

4288-408: The total number of bits used for an RGB color is typically called the color depth . Since colors are usually defined by three components, not only in the RGB model, but also in other color models such as CIELAB and Y'UV , among others, then a three-dimensional volume is described by treating the component values as ordinary Cartesian coordinates in a Euclidean space . For the RGB model, this

4355-664: Was patented by Werner Flechsig in Germany in 1938. Personal computers of the late 1970s and early 1980s, such as the Apple II and VIC-20 , use composite video . The Commodore 64 and the Atari 8-bit computers use S-Video derivatives. IBM introduced a 16-color scheme (four bits—one bit each for red, green, blue, and intensity) with the Color Graphics Adapter (CGA) for its IBM PC in 1981, later improved with

4422-541: Was realized that perceptual uniformity means the color space can no longer be a sphere. As a convention, the hue for red is set to 0° for most color spaces with a hue. In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as the CIE 1976 ( L *, a *, b *) ( CIELAB ) and 1976 ( L *, u *, v *) ( CIELUV ) color spaces, hue may be computed together with chroma by converting these coordinates from rectangular form to polar form. Hue

4489-519: Was used by other pioneers, such as the Russian Sergey Prokudin-Gorsky in the period 1909 through 1915. Such methods lasted until about 1960 using the expensive and extremely complex tri-color carbro Autotype process. When employed, the reproduction of prints from three-plate photos was done by dyes or pigments using the complementary CMY model, by simply using the negative plates of the filtered takes: reverse red gives

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