OCCT3D OCCT 8.0.1
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    Open CASCADE Technology Reference Manual 8.0.1
    Quantity_TypeOfColor.hxx File Reference

    Enumerations

    enum  Quantity_TypeOfColor {
      Quantity_TOC_RGB , Quantity_TOC_sRGB , Quantity_TOC_HLS , Quantity_TOC_CIELab ,
      Quantity_TOC_CIELch
    }
     Identifies color definition systems. More...

    Enumeration Type Documentation

    ◆ Quantity_TypeOfColor

    Identifies color definition systems.

    Enumerator
    Quantity_TOC_RGB 

    Normalized linear RGB (red, green, blue) values within range [0..1] for each component.

    Quantity_TOC_sRGB 

    Normalized non-linear gamma-shifted RGB (red, green, blue) values within range [0..1] for each component.

    Quantity_TOC_HLS 

    Hue + light + saturation components, where:

    • First component is the Hue (H) angle in degrees within range [0.0; 360.0], 0.0 being Red; value -1.0 is a special value reserved for grayscale color (S should be 0.0).
    • Second component is the Lightness (L) within range [0.0; 1.0]
    • Third component is the Saturation (S) within range [0.0; 1.0]
    Quantity_TOC_CIELab 

    CIE L*a*b* color space, constructed to be perceptually uniform for human eye. The values are assumed to be with respect to D65 2° white point.

    The color is defined by:

    • L: lightness in range [0, 100] (from black to white)
    • a: green-to-red axis, approximately in range [-90, 100]
    • b: blue-to-yellow axis, approximately in range [-110, 95]

    Note that not all combinations of L, a, and b values represent visible colors, and RGB cube takes only part of visible color space.

    When Lab color is converted to RGB, a and b components may be reduced (with the same proportion) to fit the result into the RGB range.

    Quantity_TOC_CIELch 

    CIE L*c*h* color space, same as L*a*b* in cylindrical coordinates:

    • L: lightness in range [0, 100] (from black to white)
    • c: chroma, approximately in range [0, 135], 0 corresponds to greyscale
    • h: hue angle, in range [0., 360.]

    The hue values of standard colors are approximately:

    • red at 40,
    • yellow at 103,
    • green at 136,
    • cyan at 196,
    • blue at 306,
    • magenta at 328.

    When Lch color is converted to RGB, chroma component may be reduced to fit the color into the RGB range.