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35-431: SuperPaint had the ability to capture images from standard video input or combine them with preexisting digital data. SuperPaint was also the first program to use now-ubiquitous features in common computer graphics programs such as changing hue , saturation and value of graphical data, choosing from a preset color palette, custom polygons and lines, virtual paintbrushes and pencils, and auto-filling of images. SuperPaint

70-411: A , b ) {\displaystyle (a,b)} to ( C a b , h a b ) {\displaystyle \left(C_{ab},h_{ab}\right)} is given by: C a b ∗ = a ∗ 2 + b ∗ 2 {\displaystyle C_{ab}^{*}={\sqrt {a^{*2}+b^{*2}}}} h

105-451: A b = C a b ∗ C a b ∗ 2 + L ∗ 2 100 % {\displaystyle S_{ab}={\frac {C_{ab}^{*}}{\sqrt {{C_{ab}^{*}}^{2}+{L^{*}}^{2}}}}100\%} where S a b {\displaystyle S_{ab}} is the saturation, L ∗ {\displaystyle L^{*}}

140-601: A b = atan2 ⁡ ( b ⋆ , a ⋆ ) {\displaystyle h_{ab}=\operatorname {atan2} \left({b^{\star }},{a^{\star }}\right)} and analogously for CIE LCh(uv). The chroma in the CIE LCh(ab) and CIE LCh(uv) coordinates has the advantage of being more psychovisually linear, yet they are non-linear in terms of linear component color mixing. And therefore, chroma in CIE 1976 Lab and LUV color spaces

175-671: A stimulus can be described as similar to or different from stimuli that are described as red , orange , yellow , green , blue , violet ," within certain theories of color vision . Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a color space coordinate diagram (such as a chromaticity diagram ) or color wheel , or by its dominant wavelength or by that of its complementary color . The other color appearance parameters are colorfulness , saturation (also known as intensity or chroma), lightness , and brightness . Usually, colors with

210-435: A color hexagon, similar to a trilinear plot described by Evans, Hanson, and Brewer, which may be used to compute hue from RGB . To place red at 0°, green at 120°, and blue at 240°, Equivalently, one may solve Preucil used a polar plot, which he termed a color circle. Using R, G, and B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, and B prevail, then apply

245-450: A color system with a hue was explored as early as 1830 with Philipp Otto Runge 's color sphere. The Munsell color system from the 1930s was a great step forward, as it was realized that perceptual uniformity means the color space can no longer be a sphere. As a convention, the hue for red is set to 0° for most color spaces with a hue. In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as

280-474: A reasonable predictor of saturation, and demonstrates that adjusting the lightness in CIELAB while holding ( a *, b *) fixed does affect the saturation. But the following verbal definition of Manfred Richter and the corresponding formula proposed by Eva Lübbe are in agreement with the human perception of saturation: Saturation is the proportion of pure chromatic color in the total color sensation. S

315-599: Is Δ H a b ∗ {\displaystyle \Delta H_{ab}^{*}} in CIELAB and Δ H u v ∗ {\displaystyle \Delta H_{uv}^{*}} in CIELUV. There exists some correspondence, more or less precise, between hue values and color terms (names). One approach in color science is to use traditional color terms but try to give them more precise definitions. See spectral color#Spectral color terms for names of highly saturated colors with

350-548: Is also possible — and sometimes desirable — to define a saturation-like quantity that is linearized in term of the psychovisual perception. In the CIE 1976 LAB and LUV color spaces , the unnormalized chroma is the radial component of the cylindrical coordinate CIE LCh (lightness, chroma, hue) representation of the LAB and LUV color spaces, also denoted as CIE LCh(ab) or CIE LCh for short, and CIE LCh(uv). The transformation of (

385-593: Is equal to the chroma normalized by the lightness : s u v = C u v ∗ L ∗ = 13 ( u ′ − u n ′ ) 2 + ( v ′ − v n ′ ) 2 {\displaystyle s_{uv}={\frac {C_{uv}^{*}}{L^{*}}}=13{\sqrt {(u'-u'_{n})^{2}+(v'-v'_{n})^{2}}}} where ( u n , v n ) {\displaystyle \left(u_{n},v_{n}\right)}

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420-576: Is proportional to the chroma C , {\displaystyle C,} thus the CIECAM02 definition bears some similarity to the CIELUV definition. Saturation is also one of three coordinates in the HSL and HSV color spaces . However, in the HSL color space saturation exists independently of lightness. That is, both a very light color and a very dark color can be heavily saturated in HSL; whereas in

455-468: Is quantified. The first is the simple difference between the two hue angles. The symbol for this expression of hue difference is Δ h a b {\displaystyle \Delta h_{ab}} in CIELAB and Δ h u v {\displaystyle \Delta h_{uv}} in CIELUV. The other is computed as the residual total color difference after Lightness and Chroma differences have been accounted for; its symbol

490-745: Is the chromaticity of the white point, and chroma is defined below. By analogy, in CIELAB this would yield: s a b = C a b ∗ L ∗ = a ∗ 2 + b ∗ 2 L ∗ {\displaystyle s_{ab}={\frac {C_{ab}^{*}}{L^{*}}}={\frac {\sqrt {{a^{*}}^{2}+{b^{*}}^{2}}}{L^{*}}}} The CIE has not formally recommended this equation since CIELAB has no chromaticity diagram, and this definition therefore lacks direct connection with older concepts of saturation. Nevertheless, this equation provides

525-542: Is usually based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone , or the HSL double cone as a double hexacone. The formulae used are those in the table above. One might notice that the HSL/HSV hue "circle" do not appear to all be of the same brightness. This is a known issue of this RGB-based derivation of hue. Manufacturers of pigments use the word hue, for example, "cadmium yellow (hue)" to indicate that

560-418: Is very much different from the traditional sense of "saturation". Another, psychovisually even more accurate, but also more complex method to obtain or specify the saturation is to use a color appearance model like CIECAM02. Here, the chroma color appearance parameter might (depending on the color appearance model) be intertwined with e.g. the physical brightness of the illumination or the characteristics of

595-645: The International Commission on Illumination (CIE) they respectively describe three different aspects of chromatic intensity, but the terms are often used loosely and interchangeably in contexts where these aspects are not clearly distinguished. The precise meanings of the terms vary by what other functions they are dependent on. As colorfulness, chroma, and saturation are defined as attributes of perception, they can not be physically measured as such, but they can be quantified in relation to psychometric scales intended to be perceptually even—for example,

630-493: The lightness and C a b ∗ {\displaystyle C_{ab}^{*}} is the chroma of the color. In CIECAM02 , saturation equals the square root of the colorfulness divided by the brightness : s = M Q {\displaystyle s={\sqrt {\frac {M}{Q}}}} This definition is inspired by experimental work done with the intention of remedying CIECAM97s 's poor performance. M {\displaystyle M}

665-438: The CIE 1976 ( L *, a *, b *) ( CIELAB ) and 1976 ( L *, u *, v *) ( CIELUV ) color spaces, hue may be computed together with chroma by converting these coordinates from rectangular form to polar form. Hue is the angular component of the polar representation, while chroma is the radial component. Specifically, in CIELAB while, analogously, in CIELUV where, atan2 is a two-argument inverse tangent. Preucil describes

700-472: The Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° (red, yellow, green, cyan, blue, magenta, and the colors midway between contiguous pairs) and differ by approximately 1.2° at odd integer multiples of 15° (based on the circle formula), the maximal divergence between the two. The process of converting an RGB color into an HSL color space or HSV color space

735-663: The SuperPaint configuration was an 8-bit video digitizer , and direct conversion to standard NTSC video. The system is now in the permanent collection of the Computer History Museum in Mountain View, California. Hue In color theory , hue is one of the main properties (called color appearance parameters ) of a color , defined technically in the CIECAM02 model as "the degree to which

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770-501: The black point, while lines of uniform chroma are vertical. The naïve definition of saturation does not specify its response function. In the CIE XYZ and RGB color spaces, the saturation is defined in terms of additive color mixing, and has the property of being proportional to any scaling centered at white or the white point illuminant. However, both color spaces are non-linear in terms of psychovisually perceived color differences . It

805-410: The chroma C . {\displaystyle C.} It is defined as M = C F B 0.25 , {\displaystyle M=CF_{B}^{0.25},} where F L {\displaystyle F_{L}} is dependent on the viewing condition. The saturation of a color is determined by a combination of light intensity and how much it is distributed across

840-522: The chroma scales of the Munsell system . While the chroma and lightness of an object are its colorfulness and brightness judged in proportion to the same thing ("the brightness of a similarly illuminated area that appears white or highly transmitting"), the saturation of the light coming from that object is in effect the chroma of the object judged in proportion to its lightness. On a Munsell hue page, lines of uniform saturation thus tend to radiate from near

875-410: The coordinates of the color in question, until it intersects the spectral locus . The wavelength at which the line intersects the spectrum locus is identified as the color's dominant wavelength if the point is on the same side of the white point as the spectral locus, and as the color's complementary wavelength if the point is on the opposite side. There are two main ways in which hue difference

910-437: The emitting/reflecting surface, which is more sensible psychovisually. The CIECAM02 chroma C , {\displaystyle C,} for example, is computed from a lightness J {\displaystyle J} in addition to a naively evaluated color magnitude t . {\displaystyle t.} In addition, a colorfulness M {\displaystyle M} parameter exists alongside

945-475: The formula given in the table below. In each case the formula contains the fraction M − L H − L {\displaystyle {\frac {M-L}{H-L}}} , where H is the highest of R, G, and B; L is the lowest, and M is the mid one between the other two. This is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction. Hue angles computed for

980-624: The hue from ≈ 0° (red) up to ≈ 275° (violet), and line of purples#Table of highly-saturated purple colors for color terms of the remaining part of the color wheel. Alternative approach is to use a systematic notation. It can be a standard angle notation for certain color model such as HSL/HSV mentioned above, CIELUV , or CIECAM02 . Alphanumeric notations such as of Munsell color system , NCS , and Pantone Matching System are also used. Saturation (color theory) Colorfulness , chroma and saturation are attributes of perceived color relating to chromatic intensity. As defined formally by

1015-405: The original pigmentation ingredient, often toxic, has been replaced by safer (or cheaper) alternatives whilst retaining the hue of the original. Replacements are often used for chromium , cadmium and alizarin . Dominant wavelength (or sometimes equivalent wavelength) is a physical analog to the perceptual attribute hue. On a chromaticity diagram , a line is drawn from a white point through

1050-997: The previous definitions—as well as in the HSV color space—colors approaching white all feature low saturation. The excitation purity (purity for short) of a stimulus is the difference from the illuminant's white point to the furthest point on the chromaticity diagram with the same dominant wavelength ; using the CIE 1931 color space : p e = ( x − x n ) 2 + ( y − y n ) 2 ( x I − x n ) 2 + ( y I − y n ) 2 {\displaystyle p_{e}={\sqrt {\frac {\left(x-x_{n}\right)^{2}+\left(y-y_{n}\right)^{2}}{\left(x_{I}-x_{n}\right)^{2}+\left(y_{I}-y_{n}\right)^{2}}}}} where ( x n , y n ) {\displaystyle \left(x_{n},y_{n}\right)}

1085-452: The same hue are distinguished with adjectives referring to their lightness or colorfulness - for example: "light blue", " pastel blue", "vivid blue", and "cobalt blue". Exceptions include brown , which is a dark orange . In painting , a hue is a pure pigment —one without tint or shade (added white or black pigment, respectively). The human brain first processes hues in areas in the extended V4 called globs . The concept of

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1120-443: The spectrum of different wavelengths. The purest (most saturated) color is achieved by using just one wavelength at a high intensity, such as in laser light. If the intensity drops, then as a result the saturation drops. To desaturate a color of given intensity in a subtractive system (such as watercolor ), one can add white, black, gray , or the hue's complement . Various correlates of saturation follow. In CIELUV , saturation

1155-421: The total framebuffer be implemented as a 307,200 byte shift register that shifted in synchronization with the television output signal. The primary drawback to this scheme was that memory was not random access . Rather, a given position could be accessed only when the desired scan-line and pixel time rolled around. This gave the system a maximum latency of 33 ms for writing to the framebuffer. Also included in

1190-429: Was a custom computer system built around a Data General Nova 800 minicomputer CPU and a hand-wired shift register framebuffer . This system had 311,040 bytes (303.75 KB ) of memory and was capable of storing 640 by 480 pixels of data with 8 bits of color depth . The memory was scattered across 16 circuit boards , each loaded with multiple 2- kilobit shift register chips. While workable, this design required that

1225-1012: Was also one of the first graphics programs to use a graphical user interface and was one of the earliest to feature anti-aliasing . SuperPaint was used in the mid-1970s to make custom television graphics for KQED-TV in San Francisco, and later to make technical graphics and animations for the NASA Pioneer Venus project mission in 1978. Due to differences with management at PARC, Shoup left Xerox in 1979 to found graphics company Aurora Systems, while colleague Alvy Ray Smith went to work at New York Institute of Technology . In 1980, Smith and others joined Industrial Light & Magic , George Lucas 's movie special effects firm, and this group later founded Pixar . Shoup won an Emmy Award in 1983, and an Academy Scientific Engineering Award shared with Smith and Thomas Porter in 1998, for his development of SuperPaint. The SuperPaint system

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