The VIDC1 was a Video Display Controller chip created as an accompanying chip to the ARM CPU used in Acorn Archimedes computer systems. Its successor, the VIDC20 , was later used in RiscPCs .
62-479: The VIDC1 offers colour depths of 1, 2, 4 or eight bits per colour, allowing for 2, 4, 16 and 256 colour displays (the VIDC20 can offer up to approximately 16 million colours). A colour lookup table or palette register set of 16 12-bit words was provided, offering a range of 4096 colours for each of the colours in those displays or modes employing up to 16 colours. The 12 bits were split in three 4-bit RGB values , with
124-434: A 4-bit high speed D/A converter for each of the three primary colours. However, in 256 colour modes, 4 bits of the colour data were hardware derived and could not be adjusted. The net result was 256 colours, covering a range of the 4096 available colours. Since the device had no horizontal sync interrupt, it was difficult to display additional colours by changing the palette for each scan line, but not impossible, thanks to
186-451: A 4-level alpha channel ); the Cineon file format , for example, used this. Some SGI systems had 10- (or more) bit digital-to-analog converters for the video signal and could be set up to interpret data stored this way for display. BMP files define this as one of its formats, and it is called "HiColor" by Microsoft . Video cards with 10 bits per component started coming to market in
248-456: A bit depth of 8 bits to 16 bits per sample. As of 2020, some smartphones have started using 30-bit color depth, such as the OnePlus ;8 Pro , Oppo Find X2 & Find X2 Pro, Sony Xperia 1 II , Xiaomi Mi 10 Ultra , Motorola Edge+ , ROG Phone 3 and Sharp Aquos Zero 2. Using 12 bits per color channel produces 36 bits, 68,719,476,736 colors. If an alpha channel of
310-552: A color channel is also known as radiometric resolution , especially in the context of satellite images . With the relatively low color depth, the stored value is typically a number representing the index into a color map or palette (a form of vector quantization ). The colors available in the palette itself may be fixed by the hardware or modifiable by software. Modifiable palettes are sometimes referred to as pseudocolor palettes. Old graphics chips, particularly those used in home computers and video game consoles , often have
372-412: A color cube in the palette for a direct-color system (and so all programs would use the same palette). Usually fewer levels of blue were provided than others, since the normal human eye is less sensitive to the blue component than to either red or green (two thirds of the eye's receptors process the longer wavelengths ). Popular sizes were: 4,096 colors, usually from a fully-programmable palette (though it
434-499: A contemporary laser printer) but color proved more popular. 4 colors, usually from a selection of fixed palettes. Gray-scale early NeXTstation , color Macintoshes, Atari ST medium resolution. 8 colors, almost always all combinations of full-intensity red, green, and blue. Many early home computers with TV displays, including the ZX Spectrum and BBC Micro . 16 colors, usually from a selection of fixed palettes. Used by IBM CGA (at
496-616: A culturally significant figure of the modern art movement by creating false-color paintings with screen printing techniques. Some of Warhol's most recognizable prints include a replication of Marilyn Monroe , her image based on a film frame from the movie Niagara . The subject was a sex symbol and film noir starlet whose death in 1962 influenced the artist. A series of prints were made with endearment but expose her persona as an illusion through his assembly line style of art production which are non-erotic and slightly grotesque. Using various ink color palettes, Warhol immersed himself in
558-450: A false-color image. At least two spectral bands are needed for a false-color encoding, and it is possible to combine more bands into the three visual RGB bands – with the eye's ability to discern three channels being the limiting factor. In contrast, a "color" image made from one spectral band, or an image made from data consisting of non-EM data (e.g. elevation, temperature, tissue type) is a pseudocolor image (see below). For true color,
620-419: A human observer the same way as if this same observer were to directly view the object: A green tree appears green in the image, a red apple red, a blue sky blue, and so on. Absolute true-color rendering is impossible. There are three major sources of color error ( metameric failure): The result of a metameric failure would be for example an image of a green tree which shows a different shade of green than
682-488: A process of repetition that serves to compare personas and everyday objects to the qualities of mass production and consumerism . The colors of ink were selected through experimentation of aesthetics and do not correlate to false-color rendering of the electromagnetic spectrum employed in remote sensing image processing. For years the artist continued screen printing false-color images of Marilyn Monroe, perhaps his most referenced work being Turquoise Marilyn which
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#1733106139015744-487: A proprietary video laser interface chip, VLASER6. In the Technical Publishing System, the podule was "configured specifically to drive a 300 dpi Canon CX/SX print engine directly". Unlike conventional video, each raster line produced by the print engine effectively corresponded to a single video frame having only a single scanline, with vertical synchronisation occurring repeatedly over the course of generating
806-417: A single grayscale channel or data not depicting parts of the electromagnetic spectrum (e.g. elevation in relief maps or tissue types in magnetic resonance imaging ). The concept behind true color can help in understanding false color. An image is called a true-color image when it offers a natural color rendition, or when it comes close to it. This means that the colors of an object in an image appear to
868-406: A single page. An A4 page could have a resolution of 2432 dots horizontally, reproduced in 3440 lines vertically, requiring a total of over 8 million pixels. The VIDC also supported eight-channel stereo logarithmic 8-bit PWM sound. Color depth Color depth or colour depth (see spelling differences ), also known as bit depth , is either the number of bits used to indicate
930-399: A variation of pseudo color, divides an image into a few colored bands and is (among others) used in the analysis of remote sensing images. For density slicing the range of grayscale levels is divided into intervals, with each interval assigned to one of a few discrete colors – this is in contrast to pseudo color, which uses a continuous color scale. For example, in a grayscale thermal image
992-450: A visually lossless low-latency algorithm based on predictive DPCM and YCoCg-R color space and allows increased resolutions and color depths and reduced power consumption." At WinHEC 2008, Microsoft announced that color depths of 30 bits and 48 bits would be supported in Windows 7 , along with the wide color gamut scRGB . High Efficiency Video Coding (HEVC or H.265) defines
1054-413: A yellow subpixel. However, formats and media that allow or make use of the extended color gamut are at present extremely rare. Because humans are overwhelmingly trichromats or dichromats one might suppose that adding a fourth "primary" color could provide no practical benefit. However humans can see a broader range of colors than a mixture of three colored lights can display. The deficit of colors
1116-414: Is also often used to refer to all color depths greater or equal to 24. Deep color consists of a billion or more colors. 2 is 1,073,741,824. Usually this is 10 bits each of red, green, and blue (10 bpc). If an alpha channel of the same size is added then each pixel takes 40 bits. Some earlier systems placed three 10-bit channels in a 32-bit word , with 2 bits unused (or used as
1178-554: Is assigned 5 bits, plus one unused bit (or used for a mask channel or to switch to indexed color); this allows 32,768 colors to be represented. However, an alternate assignment which reassigns the unused bit to the G channel allows 65,536 colors to be represented, but without transparency. These color depths are sometimes used in small devices with a color display, such as mobile phones, and are sometimes considered sufficient to display photographic images. Occasionally 4 bits per color are used plus 4 bits for alpha, giving 4,096 colors. Among
1240-444: Is commonly used to display three channels of data. Pseudocoloring can make some details more visible, as the perceived difference in color space is bigger than between successive gray levels alone. On the other hand, the color mapping function should be chosen to make sure the lightness of the color is still monotonic, or the uneven change would make it hard to interpret levels, for both normal and colorblind viewers. One offender
1302-421: Is only one aspect of color representation, expressing the precision with which the amount of each primary can be expressed; the other aspect is how broad a range of colors can be expressed (the gamut ). The definition of both color precision and gamut is accomplished with a color encoding specification which assigns a digital code value to a location in a color space . The number of bits of resolved intensity in
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#17331061390151364-410: Is particularly noticeable in saturated shades of bluish green (shown as the left upper grey part of the horseshoe in the diagram) of RGB displays: Most humans can see more vivid blue-greens than any color video screen can display. False color False colors and pseudo colors respectively refers to a group of color rendering methods used to display images in colors which were recorded in
1426-596: Is the commonly-used "rainbow" palette, with a back-and-forth change in lightness. (See also Choropleth map § Color progression .) A typical example for the use of pseudo color is thermography (thermal imaging), where infrared cameras feature only one spectral band and show their grayscale images in pseudo color. Another familiar example of pseudo color is the encoding of elevation using hypsometric tints in physical relief maps , where negative values (below sea level ) are usually represented by shades of blue, and positive values by greens and browns. Depending on
1488-527: Is used by virtually every computer and phone display and the vast majority of image storage formats . Almost all cases of 32 bits per pixel assigns 24 bits to the color, and the remaining 8 are the alpha channel or unused. 2 gives 16,777,216 color variations. The human eye can discriminate up to ten million colors, and since the gamut of a display is smaller than the range of human vision, this means this should cover that range with more detail than can be perceived. However, displays do not evenly distribute
1550-514: Is used, with "N" being the near-infrared spectral band (and the blue spectral band being unused) – this yields the typical "vegetation in red" false-color images. False color is used (among others) for satellite and space images: Examples are remote sensing satellites (e.g. Landsat , see example above), space telescopes (e.g. the Hubble Space Telescope ) or space probes (e.g. Cassini-Huygens ). Some spacecraft, with rovers (e.g.
1612-475: The Mars Science Laboratory Curiosity ) being the most prominent examples, have the ability to capture approximate true-color images as well. Weather satellites produce, in contrast to the spacecraft mentioned previously, grayscale images from the visible or infrared spectrum. False color has a range of scientific applications. Spacecraft often employ false-color methods to help understand
1674-747: The Nvidia Quadro graphics cards manufactured after 2006 support 30-bit deep color and Pascal or later GeForce and Titan cards when paired with the Studio Driver as do some models of the Radeon HD ;5900 series such as the HD ;5970. The ATI FireGL V7350 graphics card supports 40- and 64-bit pixels (30 and 48 bit color depth with an alpha channel). The DisplayPort specification also supports color depths greater than 24 bpp in version 1.3 through " VESA Display Stream Compression , which uses
1736-447: The RGB channels (red "R", green "G" and blue "B") from the camera are mapped to the corresponding RGB channels of the image, yielding a "RGB→RGB" mapping. For false color this relationship is changed. The simplest false-color encoding is to take an RGB image in the visible spectrum, but map it differently, e.g. "GBR→RGB". For traditional false-color satellite images of Earth a "NRG→RGB" mapping
1798-453: The category or value of one or more variables being represented. The variables are mapped to a few colors; each area contributes one data point and receives one color from these selected colors. Basically, it is density slicing applied to a pseudocolor overlay. A choropleth map of a geographic area is thus an extreme form of false color. While artistic rendition lends to subjective expression of color, Andy Warhol (1928–1987) has become
1860-485: The color gamut of a display, since it is no longer limited to the interior of a triangle formed by three primaries at its corners, e.g. the CIE 1931 color space . Recent technologies such as Texas Instruments 's BrilliantColor augment the typical red, green, and blue channels with up to three other primaries: cyan, magenta, and yellow. Cyan would be indicated by negative values in the red channel, magenta by negative values in
1922-436: The open standard image file format OpenEXR which supported 16-bit-per-channel half-precision floating-point numbers. At values near 1.0, half precision floating point values have only the precision of an 11-bit integer value, leading some graphics professionals to reject half-precision in situations where the extended dynamic range is not needed. Virtually all television displays and computer displays form images by varying
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1984-493: The visible or non-visible parts of the electromagnetic spectrum . A false-color image is an image that depicts an object in colors that differ from those a photograph (a true-color image ) would show. In this image, colors have been assigned to three different wavelengths that human eyes cannot normally see. In addition, variants of false colors such as pseudocolors , density slicing , and choropleths are used for information visualization of either data gathered by
2046-430: The 2 MHz IOC timer 1. Many demos managed to display 4096 colours on screen, or in a sense more through dithering . The timing generator was fully programmable, and could be clocked with an 8 to 24 MHz clock. Resolutions that could be supported were 1024x1024 in monochrome, 640x512 in 16 colors, or 640x256 in 256 colors. It had also one hardware 32-pixel wide sprite with unlimited height (by default used for
2108-650: The Main ;10 profile, which allows for 8 or 10 bits per sample with 4:2:0 chroma subsampling . The Main 10 profile was added at the October ;2012 HEVC meeting based on proposal JCTVC-K0109 which proposed that a 10-bit profile be added to HEVC for consumer applications. The proposal stated that this was to allow for improved video quality and to support the Rec. 2020 color space that will be used by UHDTV . The second version of HEVC has five profiles that allow for
2170-444: The ability to use a different palette per sprites and tiles in order to increase the maximum number of simultaneously displayed colors, while minimizing use of then-expensive memory (and bandwidth). For example, in the ZX Spectrum the picture is stored in a two-color format, but these two colors can be separately defined for each rectangular block of 8×8 pixels. The palette itself has a color depth (number of bits per entry). While
2232-443: The best VGA systems only offered an 18-bit (262,144 color) palette from which colors could be chosen, all color Macintosh video hardware offered a 24-bit (16 million color) palette. 24-bit palettes are nearly universal on any recent hardware or file format using them. If instead the color can be directly figured out from the pixel values, it is "direct color". Palettes were rarely used for depths greater than 12 bits per pixel, as
2294-413: The bottom 2 bits of 8-bit data, but if 16 bits were used it would lose none of the 8-bit data). In addition, digital cameras are able to produce 10 or 12 bits per channel in their raw data; as 16 bits is the smallest addressable unit larger than that, using it would make it easier to manipulate the raw data. Some systems started using those bits for numbers outside the 0–1 range rather than for increasing
2356-564: The color of a single pixel , or the number of bits used for each color component of a single pixel. When referring to a pixel, the concept can be defined as bits per pixel (bpp). When referring to a color component, the concept can be defined as bits per component , bits per channel , bits per color (all three abbreviated bpc), and also bits per pixel component , bits per color channel or bits per sample (bps). Modern standards tend to use bits per component, but historical lower-depth systems used bits per pixel more often. Color depth
2418-400: The colors in human perception space, so humans can see the changes between some adjacent colors as color banding . Monochromatic images set all three channels to the same value, resulting in only 256 different colors; some software attempts to dither the gray level into the color channels to increase this, although in modern software this is more often used for subpixel rendering to increase
2480-549: The composition of structures in the universe such as nebula and galaxies. The frequency of light emitted by different ions in space are assigned contrasting colors, allowing the chemical composition of complex structures to be better separated and visualised. The image of the Eagle Nebula above is a typical example of this; the Hydrogen and Oxygen ions have been assigned green and blue respectively. The large amounts of green and blue in
2542-763: The first hardware to use the standard were the Sharp X68000 and IBM's Extended Graphics Array (XGA). The term "high color" has recently been used to mean color depths greater than 24 bits. Almost all of the least expensive LCDs (such as typical twisted nematic types) provide 18-bit color (64×64×64 = 262,144 combinations) to achieve faster color transition times, and use either dithering or frame rate control to approximate 24-bit-per-pixel true color, or throw away 6 bits of color information entirely. More expensive LCDs (typically IPS ) can display 24-bit color depth or greater. 24 bits almost always use 8 bits each of R, G, and B (8 bpc). As of 2018, 24-bit color depth
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2604-579: The fraction. The Cineon imaging system used 10-bit professional video displays with the video hardware adjusted so that a value of 95 was black and 685 was white. The amplified signal tended to reduce the lifetime of the CRT. More bits also encouraged the storage of light as linear values, where the number directly corresponds to the amount of light emitted. Linear levels makes calculation of computer graphics much easier. However, linear color results in disproportionately more samples near white and fewer near black, so
2666-414: The green channel, and yellow by negative values in the blue channel, validating the use of otherwise fictitious negative numbers in the color channels. Mitsubishi and Samsung (among others) use BrilliantColor in some of their TV sets to extend the range of displayable colors. The Sharp Aquos line of televisions has introduced Quattron technology, which augments the usual RGB pixel components with
2728-522: The image show that there is a large amount of Hydrogen and Oxygen in the nebula. On 26 October 2004, the NASA/ESA Cassini-Huygens spacecraft captured a false-color image of Titan, Saturn's largest moon. The image was captured in Ultraviolet and Infrared wavelengths, both invisible to the human eye. In order to provide a visual representation, false color techniques were used. The infrared data
2790-590: The late 1990s. An early example was the Radius ThunderPower card for the Macintosh, which included extensions for QuickDraw and Adobe Photoshop plugins to support editing 30-bit images. Some vendors call their 24-bit color depth with FRC panels 30-bit panels; however, true deep color displays have 10-bit or more color depth without FRC. The HDMI 1.3 specification defines a bit depth of 30 bits (as well as 36 and 48 bit depths). In that regard,
2852-586: The lowest resolution), EGA , and by the least common denominator VGA standard at higher resolution. Color Macintoshes, Atari ST low resolution, Commodore 64 , and Amstrad CPCs also supported 4-bit color. 32 colors from a programmable palette, used by the Original Amiga chipset . 64 colors. Used by the Master System , Enhanced Graphics Adapter, GIME for TRS-80 Color Computer 3, Pebble Time smartwatch (64 color e-paper display), and Parallax Propeller using
2914-472: The memory consumed by the palette would exceed the necessary memory for direct color on every pixel. 2 colors, often black and white direct color. Sometimes 1 meant black and 0 meant white, the inverse of modern standards. Most of the first graphics displays were of this type, the X Window System was developed for such displays, and this was assumed for a 3M computer . In the late 1980s there were professional displays with resolutions up to 300 dpi (the same as
2976-476: The mouse pointer), where each pixel is coded in two bits: value 0 is for transparency, and the three others are freely chosen from the 4096 colour palette. Acorn also used the VIDC chip in its laser printer interface podule, which featured in its Technical Publishing System solution. The VIDC was used to generate a high-resolution monochrome signal driven by "a gated form of the synchronised laser dot clock", assisted by
3038-437: The physical properties of the object under investigation, and are not chosen to capture true-color images. In contrast to a true-color image, a false-color image sacrifices natural color rendition in order to ease the detection of features that are not readily discernible otherwise – for example the use of near infrared for the detection of vegetation in satellite images. While a false-color image can be created using solely
3100-453: The quality of 16-bit linear is about equal to 12-bit sRGB . Floating point numbers can represent linear light levels spacing the samples semi-logarithmically. Floating point representations also allow for drastically larger dynamic ranges as well as negative values. Most systems first supported 32-bit per channel single-precision , which far exceeded the accuracy required for most applications. In 1999, Industrial Light & Magic released
3162-422: The reference VGA circuit. 256 colors, usually from a fully-programmable palette: Most early color Unix workstations, Super VGA , color Macintosh , Atari TT , Amiga AGA chipset , Falcon030 , Acorn Archimedes . Both X and Windows provided elaborate systems to try to allow each program to select its own palette, often resulting in incorrect colors in any window other than the one with focus. Some systems placed
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#17331061390153224-422: The resolution. Numbers greater than 1 were for colors brighter than the display could show, as in high-dynamic-range imaging (HDRI). Negative numbers can increase the gamut to cover all possible colors, and for storing the results of filtering operations with negative filter coefficients. The Pixar Image Computer used 12 bits to store numbers in the range [-1.5, 2.5), with 2 bits for the integer portion and 10 for
3286-454: The same size is added then there are 48 bits per pixel. Using 16 bits per color channel produces 48 bits, 281,474,976,710,656 colors. If an alpha channel of the same size is added then there are 64 bits per pixel. Image editing software such as Adobe Photoshop started using 16 bits per channel fairly early in order to reduce the quantization on intermediate results (i.e. if an operation is divided by 4 and then multiplied by 4, it would lose
3348-466: The space resolution on LCD screens where the colors have slightly different positions. The DVD-Video and Blu-ray Disc standards support a bit depth of 8 bits per color in YCbCr with 4:2:0 chroma subsampling . YCbCr can be losslessly converted to RGB. MacOS refers to 24-bit colour as "millions of colours". The term true colour is sometimes used to mean what this article is calling direct colour . It
3410-406: The strength of just three primary colors : red, green, and blue. For example, bright yellow is formed by roughly equal red and green contributions, with no blue contribution. For storing and manipulating images, alternative ways of expanding the traditional triangle exist: One can convert image coding to use fictitious primaries, that are not physically possible but that have the effect of extending
3472-461: The table or function used and the choice of data sources, pseudocoloring may increase the information contents of the original image, for example adding geographic information, combining information obtained from infrared or ultra-violet light, or other sources like MRI scans. A further application of pseudocoloring is to store the results of image elaboration; that is, changing the colors in order to ease understanding an image. Density slicing ,
3534-458: The temperature values in the image can be split into bands of 2 °C, and each band represented by one color – as a result the temperature of one spot in the thermograph can be easier acquired by the user, because the discernible differences between the discrete colors are greater than those of images with continuous grayscale or continuous pseudo color. A choropleth is an image or map in which areas are colored or patterned proportionally to
3596-439: The tree itself, a different shade of red for a red apple, a different shade of blue for the blue sky, and so on. Color management (e.g. with ICC profiles ) can be used to mitigate this problem within the physical constraints. Approximate true-color images gathered by spacecraft are an example where images have a certain amount of metameric failure, as the spectral bands of a spacecraft's camera are chosen to gather information on
3658-433: The triangle to enclose a much larger color gamut. An equivalent, simpler change is to allow negative numbers in color channels, so that the represented colors can extend out of the color triangle formed by the primaries. However these only extend the colors that can be represented in the image encoding; neither trick extends the gamut of colors that can actually be rendered on a display device. Supplementary colors can widen
3720-436: The visual spectrum (e.g. to accentuate color differences), typically some or all data used is from electromagnetic radiation (EM) outside the visual spectrum (e.g. infrared , ultraviolet or X-ray ). The choice of spectral bands is governed by the physical properties of the object under investigation. As the human eye uses three spectral bands (see trichromacy for details), three spectral bands are commonly combined into
3782-440: Was mapped to red and green colors, and ultraviolet mapped to blue. A pseudocolor image (sometimes styled pseudo-color or pseudo color ) is derived from a grayscale image by mapping each intensity value to a color according to a table or function. Pseudo color is typically used when a single channel of data is available (e.g. temperature, elevation, soil composition, tissue type, and so on), in contrast to false color which
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#17331061390153844-466: Was often set to a 16×16×16 color cube). Some Silicon Graphics systems, Color NeXTstation systems, and Amiga systems in HAM mode have this color depth. RGBA4444, a related 16 bpp representation providing the color cube and 16 levels of transparency, is a common texture format in mobile graphics. In high-color systems, two bytes (16 bits) are stored for each pixel. Most often, each component (R, G, and B)
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