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The RGB color model is an additive color model in which red, green, and blue 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. Not to be confused with RGBA, a term used to mean "red-green-blue-alpha", which is not a different color model, but a extended representation where the alpha is an additional channel (not component) used for transparency in some digital image processing systems.
The main purpose of the RGB color model is to capture color images with electronic equipment in order to reproduce them later in electronic display devices. Before the electronic age, the RGB color model already had a solid theory behind, based in human perception of colors, but it was not widely used until then. Modern color photography and color films rely on sensible emulsions for more or other than red, green and blue light, so they are not RGB proper. The first commercial application of the RGB was in color TV. With dawning of the computer age and digital equipment, RGB was not only employed to capture and display, but also to store, manage and manipulate color images, both still and in motion. Color print relies on pigments using subtractive color models, which are not RGB related.
Typical RGB input devices are color TV and video cameras, drum, flat and film scanners, and CCD based digital cameras. Typical RGB output devices are TV sets of various technologies (CRT, LCD, plasma, etc.), computer and handy devices\' displays, video projectors, multicolor LED displays, large screens as JumboTron, etc.
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 historically in color image producing electronics technology.
To form a color with RGB, three monochrome light beams (one red, one green and one blue) must be superimposed over a dark screen (usually black, but it can be white in a dark room). Each of the three beams is called a component of that color, and every of them can have an arbitrary intensity, from fully off to fully on, in the mixage.
The RGB color model is additive in the sense that the intensity of an RGB constructed color is always greater or equal than the individual intensities of each of the three red, green and blue light beams employed. Thus, the higher the intensity levels of the component lights, the higher the intensity of the resultant color.
No 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. When the intensity 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 saturated depending on the difference of the strongest and weakest of the intensities of the primary colors employed.
When one of the components have the strongest intensity, the color is a hue of this primary color (redish, 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. Thus, 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 a secondary color are added together and the result is white): cyan complements red, magenta complements green and yellow complements blue.
To see how different RGB intensities combine together, here are a selected repertoire of colors and their respective relative (not absolute) intensities for each red, green and blue components:
It must be noticed that 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 exact, but relative. 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; see RGB color spaces for more details.
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.R. W. G. Hunt (2004). The Reproduction of Colour, 6th ed., Chichester UK: Wiley–IS&T Series in Imaging Science and Technology. ISBN 0-470-02425-9.
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 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 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 associated with the concept that the light is \'orange\'. In this sense, the orange appearance of objects is simply the result of light from the object entering our eye and stimulating the relevant kinds of cones simultaneously but to different degrees.
Use of 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.
A typical RGB color selector in graphic software. Every slider ranges from 0 to 255.
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.
These ranges may be quantified in several different ways:
For example, the full intensity red [_] is 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 channel | (255, 0, 0) |
| Digital 16-bit per channel | (65535, 0, 0) |
In some 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 color TV broadcasting and receiving due to cathodic ray tubes (CRT) gamma correction, for example.Edwin Paul J. Tozer (2004). Broadcast Engineer\'s Reference Book. Elsevier. Linear and nonlinear transformations are better dealed with in digital image processing when more than 8-bit per component are used, but even 8-bit are sufficient enough if some assumptions are made (as a given gamma correction value).Bernice Ellen Rogowitz and Thrasyvoulos N. Pappas (1998). Human Vision and Electronic Imaging III. SPIE.
The RGB color model mapped to a cube. Values decrease along the x-axis (red), y-axis (blue) and increase on the z-axis (green).
As colors are usually defined by three components (not only in the RGB model, but also in other color models like HSB and YUV, among others), a three-dimensional volume can be described treating the component values as a kind of coordinates in the euclidean space. For the RGB, the volume is a cube with the vertex corresponding the black in the origin of coordinates, and with incrementing intensity values running along the three axis, being the vertex corresponding white the one opposited that of the black, so the component values are treated as common cartesian coordinates.
Then, an RGB triplet (r,g,b) is here treated as the three-dimensional coordinate of the point of the given color inside the cube (including its faces). This approach allows to perform computations of color similarity of two given RGB colors by simply calculating the euclidean distance between them: the shorter the distance, the higher the similarity. Out-of-gamut computations can be performed this way, too.
The first permanent color photograph, taken by J. C. Maxwell in 1861 using three red, green and violet-blue filters.
The RGB color model is based on the Young–Helmholtz theory of trichromatic color vision (published in the first mid of the 19th century), and on James C. Maxwell\'s color triangle that elaborated that theory (circa 1860).
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.Robert Hirsch (2004). Exploring Colour Photography: A Complete Guide. Laurence King Publishing. ISBN 1856694208. Color photography by taking three separate plates were often used by pioneers (as Russian Sergey Prokudin-Gorsky in the period 1909 through 1915Photographer to the Tsar: Sergei Mikhailovich Prokudin-Gorskii Library of Congress.) and it lasts until about 1960 using the expensive and extremely complex tri-color carbro Autotype process.The Evolution of Color Pigment Printing
In pre-electronics, patents on mechanically scanned color systems exist since 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 displaying were made by mechanical means through spinning colorized wheels.John Logie Baird, Television Apparatus and the Like, U.S. patent, filed in U.K. in 1928.Baird Television: Crystal Palace Television Studios. Previous color television demonstrations in the U.K. and U.S. had been via closed circuit.
The Columbia Broadcasting System (CBS) began experimental RGB field-sequential color system in 1940. Images were electronically scanned, but it still used a moving part: the transparent RGB color wheel rotating at above 1,200 rpm synchronized in front of both the monochromatic camera and the cathode-ray tube (CRT) receiver counterpart."Color Television Success in Test," New York Times, Aug. 30, 1940, p. 21. "CBS Demonstrates Full Color Television," Wall Street Journal, Sept. 5, 1940, p. 1. "Television Hearing Set," New York Times, Nov. 13, 1940, p. 26. The world\'s first network color broadcast was aired by five CBS affiliates in 1951, using this proprietary system (incompatible with standard US black and white TV)."C.B.S. Color Video Presents a \'First\'," New York Times, June 26, 1951, p. 31. Although not used in this system, modern RGB shadow mask technology for color CRT displays was already patented by Werner Flechsig in Germany in 1938.Television Broadcasting at IEEE
The National Television System Committee (NTSC) worked in 1950–1953 to develop a color system that was compatible with existing b&w sets in the USA, with Radio Corporation of America (RCA) developing the hardware elements. The solution was to encode RGB in the so-called YIQ, a luminance-chrominance color difference signal. First commercial NTSC equipment by RCA were the TK-40/41 series of TV cameras and studio gear, and the CT-100 (nicknamed "Merrill") TV sets, based on technology developed since 1949.CT-100 Color Receiver Gallery The first publicly TV broadcast of a program using the NTSC system was made by the National Broadcasting Company (NBC) in 1953."NBC Launches First Publicly-Announced Color Television Show," Wall Street Journal, Aug 31, 1953, p. 4.
In Europe, the French SECAM color TV system was patented in 1956 and the German PAL in 1963. The both adapted some NTSC techniques to the European electronics standards, while improving some hue error problems. The color encoding signals are YUV for PAL systems and YDbDr for SECAM. The first regular color broadcasts in Europe were by the British Broadcasting Corporation (BBC) beginning on 1967, in PAL format.
First personal computers at the end of 1970\'s and first 1980\'s as those from Apple, Atari and Commodore, do not use RGB as their main method to manage colors, but composite video. IBM introduced a very simple RGB scheme 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 truecolor graphic card for PCs (the TARGA) was Truevision in 1987, but was not until the arrive of the Video Graphics Array (VGA) in 1988 that RGB became popular, mainly due to the analogic approach of the connection between the adapter and the monitor which allows virtually any RGB color combination.
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
RGB pixels in an LCD TV (on the right: an orange and a blue color; on the left: a close-up of pixels)
Close-up of red, green, and blue LEDs that conform a single pixel in a large scale LED screen.
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 LED 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.
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.
RGB is also the term to referring 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. Extra cables are sometimes needed to carry synchronizing signals. 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. 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.
A framebuffer is a digital device for computers which stores in the so-called video memory (conformed by an array of Video RAM or similar chips) the digital image to be displayed on the monitor. Driven by software, the CPU or other speciallized chips write the apropriate bytes in the video memory to conform the image, which an electronic video generator sends to the monitor. Modern systems encode pixel color values by devoting some bits groupings for each of the RGB separate components. RGB information can be either carried by the pixel bits themselves or in a separate Color Look-Up Table (CLUT) if indexed color graphic modes are used.
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 the Digital representations section below). With this system, 16,777,216 (2563 or 224) discrete combinations of R, G and B values are allowed, providing thousands of different (though not necessarily distinguishable) hue, saturation, and lightness shades.
In classic cathode ray tube (CRT) devices, the bright of a given point over the phosphorescent screen due to the impact of accelerated electrons is not proportional to the voltage applied to electrons in their RGB electron guns, but usually lesser. The amount of this deviation is known as its gamma value (), the argument for an exponential math function which closely describes this behaviour. The linear response is given by a gamma value of 1.0, but actual CRT nonlinearity have a gamma value around 2.
Then, the intensity of the color output on CRT 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 thru Digital-to-Analog Converters—DAC). 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 that when displaying the full (1.0, 1.0, 1.0), instead of at 50%.Steve Wright (2006). Digital Compositing for Film and Video. Focal Press. ISBN 024080760X. To obtain the correct response, a gamma correction must be performed, which is part of the color calibration process of the device. It must be noticed that gamma nonlinearity is not exclusive of RGB color TV, but it affects black-and-white TV as well. In standard color TV, signals are already broadcasted in a gamma-compensated fashion by TV stations.
Display technologies different than CRT (as LCD, plasma, LED, etc.) may behave nonlinearly in different ways. When they are intended to display standard TV and video shows, they are built in a such way that they behave in gamma like an older CRT TV set. In digital image processing, gamma-correction must applied either by the hardware display and/or by the software packages used if the display is a CRT or it behaves in gamma like a CRT.
Other input/output RGB devices may have also nonlinear responses, more or less related with the gamma function depending on the technology employed. In any case, nonlinearity (both 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.
The Bayer arrangement of color filters on the pixel array of an digital image sensor
In color television and video cameras manufactured before the 1990\'s, the incoming light was separated by prisms 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 CTR displays.
With the arriving of commercially viable Charge-Coupled Device (CCD) technology in the 1980\'s, 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 cameras for domestic use until convert them in handy and full camcorders. Current webcams and mobile phones with built-in 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 is given the double more detectors than red and blue (ratio 1:2:1) in order to achieve higher luminance resolution than chrominance resolution. The sensor have 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.
In computing, a 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 supports RGB color. They can be considered the sucessors of early telephotography input devices, which were able to send consecutive scan lines as a linear analog AM signal thru standard telephonic (voice) lines to appropriate receptors; this system was in use in press since 1920\'s to mid 1990\'s. Color telephotographs were sent as three separated RGB filtered images consecutively.
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 tube as the image sensor. Early color film scanners used an halogen lamp and a three RGB filter color 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 as color LEDs.
| Pixel color depth |
|---|
| Related |
|
RGB color model |
The RGB color model is the most common way to encode color in computing, and several different binary 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 form 0 to a some power of two minus one (2n – 1) to fit them into some bit groupings.
As usual in computing, the values can be represented either in decimal and in hexadecimal notation as well, as is the case of HTML colors text-encoding convention.
RGB values encoded in 24 bits per pixel (bpp) are specified using three 8-bit unsigned integers (0 through 255) representing the intensities of red, green, and blue (usually in that order, but sometimes in BGR order). This representation is the current mainstream standard representation for the so-called Truecolor and common color interchange in image file formats such as JPEG or TIFF. It allows more than 16.7 millions of different combinations (hence the term millions of colors in colloquial parlance when referring this), many of them indistinguishable to the human eye.
The following image shows the three "fully saturated" faces of a 24-bpp RGB cube, unfolded into a plane:
| yellow (255,255,0) | green (0,255,0) | cyan (0,255,255) | |
| red (255,0,0) | 
| blue (0,0,255) | |
| red (255,0,0) | magenta (255,0,255) |
The above definition uses a convention known as full-range RGB. Color values are also often scaled from and to the range 0.0 through 1.0, specially they are mapped from/to other color models and/or encodings.
Full-range RGB using eight bits per primary can represent up to 256 shades of white-grey-black, 255 shades of red, green, and blue (and equal mixtures of those), but fewer shades of other hues. The 256 levels may not represent equally spaced intensities, due to gamma correction if the file format uses explicitly this encoding.
This representation cannot offer the exact mid point 127.5, nor other non-integer values, as bytes do not hold fractional values, so these need to rounded or truncated to a nearby integer value.About roundoff errors in color conversion in Adobe tools. For example, Microsoft considers the color "medium gray"About Microsoft Windows and palettes. to be the (128,128,128) RGB triplet in its default palette. The effect of such quantization (for every value, not only the midpoint) is usually not noticeable, but may build up in repeated editing operations or colorspace conversions,Wladyslaw Wadysaw (ed.) (2001). Computer Analysis of Images and Patterns: 9th International Conference, CAIP 2001. Springer. ISBN 3540425136. no matter what degree of precision is used.
Typically, RGB for digital video is not full range. Instead, video RGB uses a convention with scaling and offsets such that (16, 16, 16) is black, (235, 235, 235) is white, etc. For example, these scalings and offsets are used for the digital RGB definition in CCIR 601.
The so-called 32 bpp display graphic mode is identical in precision to the 24 bpp mode; there are still only eight bits per component, and the eight extra bits are often not used at all. The reason for the existence of the 32 bpp mode is the higher speed at which most modern 32-bit (and better) hardware can access data that is aligned to byte addresses evenly divisible by a power of two, compared to data not so aligned.
Some graphics hardware allows the unused byte into the 32-bit mode to be used as an 8-bit paletted overlay. A certain palette entry (often 0 or 255) is designated as being transparent, i.e., where the overlay is this value the truecolor image is shown. Otherwise the overlay value is looked up in the palette and used. This allows for GUI elements (such as menus or the mouse cursor) or information to be overlayed over a truecolor image without modifying it. When the overlay needs to be removed, it is simply cleared to the transparent value and the truecolor image is displayed again. This feature was often found on graphics hardware for Unix workstations in the 90s and later on some PC graphics cards (most notably those by Matrox). However, PC graphics cards (and the systems they are used in) now have plentiful memory to use as a backing store and this feature has mostly disappeared.
With the need for compositing images came a variant of 24-bit RGB which includes an extra 8-bit channel for transparency, thus resulting also in a 32-bit format. The transparency channel is commonly known as the alpha channel, so the format is named RGBA. Note again that since it does not change anything in the RGB model, RGBA is not a distinct color model, it is only a file format which integrates transparency information along with the color information in the same file. This allows for alpha blending of the image over another, and is a feature of the PNG format. (Note: RGBA is not the only method to have transparency in graphics. See Transparency (graphic) for alternatives.)
High precision color management typically uses up to 16 bits per component, resulting in 48 bpp. This makes it possible to represent 65,536 tones of each color component instead of 256. This is primarily used in professional image editing, like Adobe Photoshop for maintaining greater precision when a sequence of more than one image filtering algorithms is used on the image. With only 8 bit per component, rounding errors tend to accumulate with each filtering algorithm that is employed, distorting the end result. Sometimes also called 16-bit mode due to the precision by component, not to be confused with 16-bit Highcolor which is a more limited representation (see below).
A 16-bit mode known as Highcolor, in which there are either 5 bits per color, called 555 mode (32,768 total colors), or the same with an extra bit for green (because the green component contributes most to the brightness of a color in the human eye), called 565 mode (65,535 colors). (In general, a good RGB representation needs 1 bit more for red than blue and 1 more bit for green. Cowlishaw, M. F. (1985). "Fundamental requirements for picture presentation" (PDF). Proc. Society for Information Display 26 (2): 101–107. , but this can not be fully achieved within a 16-bit word.) This was the high-end for some display adapters for personal computers during the 1990\'s, but today is considered slighty obsolete in favour of the 24 or 32 bpp graphic modes. It is still in use in many devices with color screens as cell phones, digital cameras, personal digital assistants (PDA) and portable videogame consoles.
Display adapters and image file formats using indexed color techniques limit the simultaneously available colors per image up to 256, 8 bits per pixel. The selected colors are arranged into a palette, and the actual image pixels values do not represent RGB triplets, but mere indices into the palette, which in turn stores the 24-bit RGB triplets for every color in the image, so colors are addressed indirectly.
Every image can have its own color selection (or adaptative palette) when indexed color is employed. But this scheme has the inconvenience that two or more indexed color images with incompatible palettes cannot be properly displayed simultaneously where the 256-color limitation is imposed by the display adapter\'s hardware.
One solution is to use an intermediate master palette which comprises a full RGB selection with limited levels to the red, green, and blue components, in order to fit it at all within 256 color entries.
Usual limited RGB repertoires include 6×6×6 levels with 216 combinations (the Web colors case), 6×7×6 levels with 252 combinations, 6×8×5 levels with 240 combinations and 8×8×4 levels with the full 256 combinations (visit the RGB arrangements section of the List of palettes article for color charts and samples).
The minimum RGB binary representation is 3-bit RGB, one bit per component. Typical for early color terminals in the 1970\'s, it is still used today with the Teletext TV retrieval service.
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.
In short, the web-safe color palette consists of the 216 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). Clearly, 6 cubed = 216. 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 color palette for a visual confirmation that the majority of the colors produced are very dark, or see Xona.com Color List for a side by side comparison of proper colors next to their equivalent lacking proper gamma correction.
The RGB color model for HTML was formally adopted as an Internet standard in HTML 3.2, however it had been in use for some time before that.
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 spaces (RGB and others, as 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.
All luminance-chrominance formats used in the different TV and video standards as YIQ for NTSC, YUV for PAL, YDbDr for SECAM, and YPbPr for composite video are color difference signals in what RGB color images can be encoded for broadcasting/recording and later decoded into RGB again to display them.
Current high efficient digital color image data compression schemes as JPEG and MPEG store RGB color internally in YCbCr format. Due to the lesser data bandwith that those color difference signals need compared to RGB signals, the use of YCbCr allows to perform lossy subsampling with the chroma channels (typically to 4:2:2 or 4:1:1 ratios), which it aids to reduce the resultant file size.
Adobe Photoshop uses the Lab color space as an intermediate color space when performing color transformations between RGB and other color spaces as CMYK.
| Color space | |
|---|---|
| List of color spaces · Color models | |
| CIE | CIE XYZ · CIELAB (L*a*b*) · CIELUV (L*u*v*) · CIE YUV (Yuv) · CIEUVW (U*V*W*) |
| RGB | RGB color spaces · sRGB · Adobe RGB · Adobe Wide Gamut RGB · ProPhoto RGB |
| YUV | YUV (PAL) · YDbDr (SECAM) · YIQ (NTSC) · YCbCr · YPbPr · xvYCC |
| Other | HSL and HSV · CMYK · RYB · Munsell color system |
| See Color vision for the vision capacities of organisms or machines. | |
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