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Color model based on red, green, and blue

"RGB" redirects here. For other uses, see RGB (disambiguation).

Not to be confused with RBG.

The RGB color model fryst vatten an additivecolor model^[1] in which the red, green and blueprimary colors of light are added tillsammans 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.^[2]

The main purpose of the RGB color model fryst vatten 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 the electronic age, the RGB color model already had a solid theory behind it, based in human observation of colors.

RGB fryst vatten 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 the same device over time.

Thus an RGB value does not define the same color across devices without some kind of color management.^[3][4]

Typical RGB input devices are color TV and film 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, film projectors, multicolor LED displays and large screens such as the Jumbotron.

The RGB color model is an additive color model [1] in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors

Color printers, on the other grabb, are not RGB devices, but subtractive color devices typically using the CMYK color model.

Additive colors

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To form eller gestalt a color with RGB, three light beams (one red, one green, and one blue) must be superimposed (for example bygd emission from a black screen or bygd reflection from a vit screen).

Each of the three beams fryst vatten called a component of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture.

The RGB color model fryst vatten 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 man up a resulting, total spectrum.^[5][6]This fryst vatten 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 the light beneath which we see them.

In the additive model, if the resulting spectrum, e.g. of superposing three colors, fryst vatten flat, vit color fryst vatten perceived bygd the human eye upon direkt incidence on the retina. This fryst vatten in kraftfull contrast to the subtractive model, where the perceived resulting spectrum fryst vatten 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 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 fryst vatten 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 the black), and full intensity of each gives a white; the quality of this vit depends on the natur of the primary light sources, but if they are properly balanced, the result fryst vatten a neutral vit matching the system's vit point. When the intensities for all the components are the same, the result fryst vatten a shade of gray, darker or lighter depending on the intensity.

When the intensities are different, the result fryst vatten 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 fryst vatten a hue nära this primary color (red-ish, green-ish, or blue-ish), and when two components have the same strongest intensity, then the color fryst vatten a hue of a secondary color (a shade of cyan, magenta or yellow).

A secondary color fryst vatten formed bygd the sum of two primary colors of lika intensity: cyan fryst vatten green+blue, magenta fryst vatten blue+red, and yellow fryst vatten red+green. Every secondary color fryst vatten the complement of one primary color: cyan complements red, magenta complements green, and yellow complements blue. When all the primary colors are mixed in lika intensities, the result fryst vatten vit.

The RGB color model itself does not define what fryst vatten meant bygd red, green, and blue colorimetrically, and so the results of blandning 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.

Physical principles for the choice of red, green, and blue

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The choice of primary colors fryst vatten related to the physiology of the human eye; good primaries are stimuli that maximize the difference between the responses of the geometri cells of the human retina to light of different wavelengths, and that thereby man a large color triangle.^[7]

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 nära 570 nm, 540 nm and 440 nm, respectively^[7]).

The difference in the signals received from the three kinds allows the brain to differentiate a bred skala of different colors, while being most sensitive (overall) to yellowish-green light and to differences between hues in the green-to-orange område.

As an example, suppose that light in the apelsinfärg 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 bygd the brain, and this difference fryst vatten the grund of our observation of apelsinfärg. Thus, the apelsinfärg 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 the three primary colors fryst vatten not sufficient to reproduce all colors; only colors within the color triangle defined bygd the chromaticities of the primaries can be reproduced bygd additive blandning of non-negative amounts of those colors of light.^{[7][page needed]}

History of RGB color model theory and usage

[edit]

The RGB color model fryst vatten based on the Young–Helmholtz theory of trichromatic color framtidsperspektiv, developed bygd Thomas ung 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).

Photography

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The first experiments with RGB in early color photography were made in 1861 bygd Maxwell himself, and involved the process of combining three color-filtered separate takes.^[1] 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 bygd taking three separate plates was used bygd other pioneers, such as the Russian Sergey Prokudin-Gorsky in the period 1909 through 1915.^[8] Such methods lasted until about 1960 using the expensive and extremely complex tri-color carbroAutotype process.^[9]

When employed, the reproduction of prints from three-plate photos was done bygd dyes or pigments using the complementary CMY model, bygd simply using the negativ plates of the filtered takes: reverse red gives the cyan tallrik, and so on.

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 Russia. The color TV pionjär 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 bygd spinning colorized wheels.^[10][11]

The Columbia Broadcasting struktur (CBS) began an experimental RGB field-sequential color struktur in 1940.

Images were scanned electrically, but the struktur still used a moving part: the tydlig RGB color wheel rotating at above 1,200 rpm in synchronism with the lodrät scan. The camera and the cathode-ray tube (CRT) were both monochromatic. Color was provided bygd color wheels in the camera and the receiver.^[12][13][14] 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 maskering technology for color CRT displays was patented bygd Werner Flechsig in Germany in 1938.^[15]

Personal computers

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Personal computers of the late 1970s and early 1980s, such as the Apple II and VIC-20, use composite film. 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 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 ankomst of the film Graphics Array (VGA) in 1987 that RGB became popular, mainly due to the motsvarande signals in the connection between the adapter and the monitor which allowed a very bred range of RGB colors.

Actually, it had to wait a few more years because the original VGA kort were palette-driven just like EGA, although with more freedom than VGA, but because the VGA connectors were motsvarande, later variants of VGA (made bygd various manufacturers beneath the informal name Super VGA) eventually added true-color. In 1992, magazines heavily advertised true-color Super VGA hardware.

Varje bildelement i en datorskärm eller TV består av tre delar som representerar varsin färg

RGB devices

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RGB and displays

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One common application of the RGB color model fryst vatten 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 fryst vatten built bygd driving three small and very close but still separated RGB light sources. At common viewing distance, the separate sources are indistinguishable, which the eye interprets as a given solid color. All the pixels tillsammans 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 the inherent nonlinearity of some devices, such that the intended intensities are reproduced on the display.

The Quattron released bygd skarp uses RGB color and adds yellow as a sub-pixel, supposedly allowing an increase in the number of available colors.

Video electronics

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Main article: Component film § RGB motsvarande component video

RGB fryst vatten also the begrepp referring to a type of component film meddelande used in the film electronics industry.

It consists of three signals—red, green, and blue—carried on three separate cables/pins. RGB meddelande formats are often based on modified versions of the RS-170 and RS-343 standards for monochrome film. This type of film meddelande fryst vatten widely used in europe since it fryst vatten the best quality meddelande that can be carried on the standard SCART connector.^[16][17] This meddelande fryst vatten known as RGBS (4 BNC/RCA terminated cables exist as well), but it fryst vatten 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 lodrät sync signals.

Outside europe, RGB fryst vatten not very popular as a film meddelande format; S-Video takes that prick in most non-European regions. However, almost all computer monitors around the world use RGB.

Video framebuffer

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A framebuffer fryst vatten a digital device for computers which stores uppgifter in the so-called video memory (comprising an array of film RAM or similar chips).

This information goes either to three digital-to-analog converters (DACs) (for motsvarande monitors), one per primary color or directly to digital monitors. Driven bygd software, the centralenhet i en dator (or other specialized chips) write the appropriate bytes into the film memory to define the image. Modern systems koda pixel color values bygd devoting eight bits to each of the R, G, and B components.

RGB data can be either carried directly bygd the pixel bits themselves or provided bygd a separate color look-up table (CLUT) if indexed color graphic modes are used.

A CLUT fryst vatten 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 fryst vatten much like a palette of colors. Image uppgifter 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.

Some film applications store such palettes in PAL files (Age of Empires game, for example, uses over half-a-dozen^[18]) and can combine CLUTs on screen.

RGB24 and RGB32

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 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 fryst vatten that an indexed-color image en samling dokument eller en elektronisk lagring av data can be significantly smaller than it would be with only 8 bits per pixel for each primary.

Modern storage, however, fryst vatten far less costly, greatly reducing the need to minimize image en samling dokument eller en elektronisk lagring av data storlek.

bygd using an appropriate combination of red, green, and blue intensities, many colors can be displayed.

RGB står för Röd, Grön, Blå och utgår från den additiva färgmodellen

Current typical display adapters use up to 24-bits of kunskap for each pixel: 8-bit per component multiplied bygd three components (see the Numeric representations section below (24bits = 256³, each primary value of 8 bits with values of 0–255). With this struktur, 16,777,216 (256³ or 2²⁴) 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 a fourth greyscale color kanal 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 kunskap see High Dynamic Range (HDR) imaging.

Nonlinearity

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Main article: Gamma correction

In classic CRT devices, the brightness of a given point over the fluorescent screen due to the impact of accelerated electrons fryst vatten 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 fryst vatten known as its gamma value (), the argument for a power lag function, which closely describes this behavior. A linear response fryst vatten given bygd 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 fryst vatten not directly proportional to the R, G, and B applied electric signals (or en samling dokument eller en elektronisk lagring av data uppgifter 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%.^[19] To obtain the correct response, a gamma correction fryst vatten used in encoding the image information, 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.

RGB and cameras

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In color television and film cameras manufactured before the 1990s, the incoming light was separated bygd prisms and filters into the three RGB primary colors feeding each color into a separate film 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 ankomst 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 bygd Sony), simplifying and even removing the intermediate optics, thereby reducing the storlek of home film 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 fryst vatten given twice as many detectors as red and blue (ratio 1:2:1) in beställning to achieve higher luminance upplösning than chrominance upplösning.

The sensor has a grid of red, green, and blue detectors arranged so that the first row fryst vatten RGRGRGRG, the next fryst vatten GBGBGBGB, and that sequence fryst vatten repeated in subsequent rows. For every kanal, missing pixels are obtained bygd inskjutning in the demosaicing process to build up the complete image. Also, other processes used to be applied in beställning to map the camera RGB measurements into a standard color space as sRGB.

RGB and scanners

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In computing, an image scanner fryst vatten a device that optically scans images (printed ord, handwriting, or an object) and converts it to a digital image which fryst vatten transferred to a computer. Among other formats, flat, drum and bio 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 lines as analogamplitude 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 the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. Early color rulle 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 bio, this technology was later replaced bygd non-heating light sources such as color LEDs.

Numeric representations

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#FFCCCC	#FFC0C0	#FF9999	#FF8080	#FF6666	#FF4040	#FF3333	#FF0000
#FFE5CC	#FFE0C0	#FFCC99	#FFC080	#FFB266	#FFA040	#FF9933	#FF8000
#FFFFCC	#FFFFC0	#FFFF99	#FFFF80	#FFFF66	#FFFF40	#FFFF33	#FFFF00
#FFFFE5	#FFFFE0	#FFFFCC	#FFFFC0	#FFFFB2	#FFFFA0	#FFFF99	#FFFF80
#E5FFCC	#E0FFC0	#CCFF99	#C0FFA0	#B2FF66	#A0FF40	#99FF33	#80FF00
#CCFFCC	#C0FFC0	#99FF99	#80FF80	#66FF66	#40FF40	#33FF33	#00FF00
#E5FFE5	#E0FFE0	#CCFFCC	#C0FFC0	#B2FFB2	#A0FFA0	#99FF99	#80FF80
#CCE5CC	#C0E0C0	#99CC99	#80C080	#66B266	#40A040	#339933	#008000
#CCFFE5	#C0FFE0	#99FFCC	#80FFC0	#66FFB2	#40FFA0	#33FF99	#00FF80
#CCFFFF	#C0FFFF	#99FFFF	#80FFFF	#66FFFF	#40FFFF	#33FFFF	#00FFFF
#E5FFFF	#E0FFFF	#CCFFFF	#C0FFFF	#B2FFFF	#A0FFFF	#99FFFF	#80FFFF
#CCE5E5	#C0E0E0	#99CCCC	#80C0C0	#66B2B2	#40A0A0	#339999	#008080
#CCE5FF	#C0E0FF	#99CCFF	#80C0FF	#66B2FF	#40A0FF	#3399FF	#0080FF
#CCCCFF	#C0C0FF	#9999FF	#8080FF	#6666FF	#4040FF	#3333FF	#0000FF
#CCCCE5	#C0C0E0	#9999CC	#8080C0	#6666B2	#4040A0	#333399	#000080
#E5E5FF	#E0E0FF	#CCCCFF	#C0C0FF	#B2B2FF	#A0A0FF	#9999FF	#8080FF
#E5CCFF	#E0C0FF	#CC99FF	#C080FF	#B266FF	#A040FF	#9933FF	#8000FF
#E5CCE5	#E0C0E0	#CC99CC	#C080C0	#B266B2	#A040A0	#993399	#800080
#FFCCFF	#FFC0FF	#FF99FF	#FF80FF	#FF66FF	#FF40FF	#FF33FF	#FF00FF
#FFE5FF	#FFE0FF	#FFCCFF	#FFC0FF	#FFB2FF	#FFA0FF	#FF99FF	#FF80FF
#FFCCE5	#FFC0E0	#FF99CC	#FF80C0	#FF66B2	#FF40A0	#FF3399	#FF0080
#FFE5E5	#FFE0E0	#FFCCCC	#FFC0C0	#FFB2B2	#FFA0A0	#FF9999	#FF8080
#E5CCCC	#E0C0C0	#CC9999	#C08080	#B26666	#A04040	#993333	#800000
#E5E5CC	#E0E0C0	#CCCC99	#C0C080	#B2B266	#A0A040	#999933	#808000
#E5E5E5	#E0E0E0	#CCCCCC	#C0C0C0	#B2B2B2	#A0A0A0	#999999	#808080

#FF0000	#CC0000	#C00000	#990000	#800000	#660000	#400000	#330000
#FF8000	#CC6600	#C06000	#994C00	#804000	#663300	#402000	#331900
#FFFF00	#CCCC00	#C0C000	#999900	#808000	#666600	#404000	#333300
#FFFF80	#CCCC66	#C0C060	#99994C	#808040	#666633	#404020	#333319
#80FF00	#66CC00	#60C000	#4C9900	#408000	#336600	#204000	#193300
#00FF00	#00CC00	#00C000	#009900	#008000	#006600	#004000	#003300
#80FF80	#66CC66	#60C060	#4C994C	#408040	#336633	#204020	#193319
#008000	#006600	#006000	#004C00	#004000	#003300	#002000	#001900
#00FF80	#00CC66	#00C060	#00994C	#008040	#006633	#004020	#003319
#00FFFF	#00CCCC	#00C0C0	#009999	#008080	#006666	#004040	#003333
#80FFFF	#66CCCC	#60C0C0	#4C9999	#408080	#336666	#204040	#193333
#008080	#006666	#006060	#004C4C	#004040	#003333	#002020	#001919
#0080FF	#0066CC	#0060C0	#004C99	#004080	#003366	#002040	#001933
#0000FF	#0000CC	#0000C0	#000099	#000080	#000066	#000040	#000033
#000080	#000066	#000060	#00004C	#000040	#000033	#000020	#000019
#8080FF	#6666CC	#6060C0	#4C4C99	#404080	#333366	#202040	#191933
#8000FF	#6600CC	#6000C0	#4C0099	#400080	#330066	#200040	#190033
#800080	#660066	#600060	#4C004C	#400040	#330033	#200020	#190019
#FF00FF	#CC00CC	#C000C0	#990099	#800080	#660066	#400040	#330033
#FF80FF	#CC66CC	#C060C0	#994C99	#804080	#663366	#402040	#331933
#FF0080	#CC0066	#C00060	#99004C	#800040	#660033	#400020	#330019
#FF8080	#CC6666	#C06060	#994C4C	#804040	#663333	#402020	#331919
#800000	#660000	#600000	#4C0000	#400000	#330000	#200000	#190000
#808000	#666600	#606000	#4C4C00	#404000	#333300	#202000	#191900
#808080	#666666	#606060	#4C4C4C	#404040	#333333	#202020	#191919

A color in the RGB color model fryst vatten described bygd indicating how much of each of the red, green, and blue fryst vatten included.

The color fryst vatten expressed as an RGB triplet (r,g,b), each component of which can vary from zero to a defined maximum value.

Som hörs på namnet beskriver signalen hur en bild ser ut genom att ange hur starkt de respektive färgerna ska lysa

If all the components are at zero the result fryst vatten black; if all are at maximum, the result fryst vatten the brightest representable vit.

These ranges may be quantified in several different ways:

• From 0 to 1, with any fractional value in between. This representation fryst vatten used in theoretical analyses, and in systems that use floating point representations.
• Each color component value can also be written as a percentage, from 0% to 100%.
• In computers, the component values are often stored as unsigned 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.

• High-end digital image redskap 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, bygd 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).

For example, brightest saturated red fryst vatten written in the different RGB notations as:

Notation	RGB triplet
Arithmetic	(1.0, 0.0, 0.0)
Percentage	(100%, 0%, 0%)
Digital 8-bit per kanal	(255, 0, 0) #FF0000 (hexadecimal)
Digital 12-bit per kanal	(4095, 0, 0) #FFF000000
Digital 16-bit per kanal	(65535, 0, 0) #FFFF00000000
Digital 24-bit per kanal	(16777215, 0, 0) #FFFFFF000000000000
Digital 32-bit per kanal	(4294967295, 0, 0) #FFFFFFFF0000000000000000

In many environments, the component values within the ranges are not managed as linear (that fryst vatten, 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.^[20] 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 fryst vatten used.^[21]

Following fryst vatten the mathematical relationship between RGB space to HSI space (hue, saturation, and intensity: HSI color space):

If , then .

Color depth

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Main article: Color depth

The RGB color model fryst vatten one of the most common ways to koda color in computing, and several different digital representations are in use.

The main characteristic of all of them fryst vatten the quantization of the possible values per component (technically a sample ) bygd using only integer numbers within some range, usually from 0 to some power of two minus one (2ⁿ − 1) to passform 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 fryst vatten typically called the color depth.

Geometric representation

[edit]

See also: RGB color spaces

Since colors are usually defined bygd 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-dimensionalvolume fryst vatten described bygd treating the component values as ordinary Cartesian coordinates in a Euclidean space.

For the RGB model, this fryst vatten represented bygd a cube using non-negative values within a 0–1 range, assigning black to the ursprung at the vertex (0, 0, 0), and with increasing intensity values running along the three axes up to vit 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 the color similarity of two given RGB colors bygd simply calculating the distance between them: the shorter the distance, the higher the similarity. Out-of-gamut computations can also be performed this way.

Colors in web-page design

[edit]

Main article: Web colors

Initially, the limited color depth of most film hardware led to a limited color palette of 216 RGB colors, defined bygd the Netscape Color Cube.

The web-safe color palette consists of the 216 (6³) 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 fryst vatten only: 0%, 2%, 10%, 28%, 57%, 100%. See the actual web safe color palette for a visual confirmation that the majority of the colors produced are very dark.^[22]

With the predominance of 24-bit displays, the use of the full 16.7 million colors of the HTML RGB color code no längre poses problems for most viewers.

The sRGB color space (a device-independent color space^[23]) for HTML was formally adopted as an Internet standard in HTML 3.2,^[24][25] though it had been in use for some time before that. All images and colors are interpreted as being sRGB (unless another color space fryst vatten specified) and all modern displays can display this color space (with color management being built in into browsers^[26][27] or operating systems^[28]).

The syntax in CSS is:

rgb(#,#,#)

where # equals the proportion of red, green, and blue respectively.

Den vanliga VGA-monitorkabeln till en datorskärm skickar just denna typ av signal tillsammans med synksignaler

This syntax can be used after such selectors as "background-color:" or (for text) "color:".

Wide skala color fryst vatten possible in modern CSS,^[29] being supported bygd all major browsers since 2023.^[30][31][32]

For example, a color on the DCI-P3 color space can be indicated as :

color(display-p3 # # #)

where # equals the proportion of red, green, and blue in 0.0 to 1.0 respectively.

Color management

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Main article: Color management

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 tydlig conversions between device-independent (sRGB, XYZ, L*a*b*)^[23] and device-dependent color spaces (RGB and others, as CMYK for color printing) during a typical production cycle, in beställning 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 skala fryst vatten 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.

ICC profil compliant applications, such as Adobe Photoshop, use either the Lab color space or the CIE 1931 color space as a Profile Connection Space when translating between color spaces.^[33]

RGB model and luminance–chrominance formats relationship

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All luminance–chrominance formats used in the different TV and film standards such as YIQ for NTSC, YUV for PAL, YD_BD_R for SECAM, and YP_BP_R for component film use color difference signals, bygd which RGB color images can be encoded for broadcasting/recording and later decoded into RGB igen 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 uppgifter bandwidth compared to full RGB signals.

Similarly, current high-efficiency digital color image information compression schemes such as JPEG and MPEG store RGB color internally in YC_BC_R format, a digital luminance–chrominance format based on YP_BP_R.

The use of YC_BC_R also allows computers to perform lossysubsampling with the chrominance channels (typically to 4:2:2 or 4:1:1 ratios), which reduces the resultant en samling dokument eller en elektronisk lagring av data storlek.

See also

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References

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External links

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