Color values

Single colors have value types of their own, in the Meziantou.Framework.Imaging namespace. Use them to build a palette, find a lighter tint, measure how different two colors look, or read the colors of a style sheet. They are immutable readonly structs of double components, and their operations allocate nothing except the strings they format.

Convert, compare and mix colors

public static (string Lab, double Difference, Rgba32[] Palette, Rgba32 Tint, Rgba32 InDisplayP3) DescribeColors()
{
    // Colors of CSS, as sRGB colors: hexadecimal, rgb(), hsl(), hwb(), lab(), lch(), oklab() and oklch()
    var brand = Rgba32.ParseCss("oklch(62% 0.2 29)");
    var accent = Rgba32.ParseCss("#2A9D8F");

    // CIELAB, relative to D50 as in CSS, and its CSS notation
    var lab = CieLab.FromRgb(brand);
    var labText = lab.ToCssString();

    // How different two colors look: about 1 is a just noticeable difference
    var difference = ColorDifference.DeltaE2000(lab, CieLab.FromRgb(accent));

    // Five colors evenly spaced in Oklch, from one color to the other along the shorter arc of hues
    var from = Oklch.FromRgb(brand);
    var to = Oklch.FromRgb(accent);
    var palette = new Rgba32[5];
    for (var i = 0; i < palette.Length; i++)
    {
        palette[i] = Oklch.Lerp(from, to, i / 4.0).ToRgba32();
    }

    // A lighter tint of the same hue and saturation
    var hsl = Hsl.FromRgb(brand);
    var tint = new Hsl(hsl.H, hsl.S, Math.Min(1, hsl.L + 0.2)).ToRgba32();

    // The same color in the samples of a Display P3 image, which its CICP description gives
    var displayP3 = RgbColorSpace.FromCicp(new CicpColorDescription(12, 13, 0, fullRange: true));
    var inDisplayP3 = lab.ToRgba32(displayP3);
    return (labText, difference, palette, tint, inDisplayP3);
}

Each type converts from and to Rgba32 and Rgba64 (FromRgb, ToRgba32, ToRgba64).

RGB values have a color space

FromRgb, ToRgba32 and ToRgba64 take an RgbColorSpace, which is sRGB by default:

• Create a color space once and reuse it.
• Alpha is not a color coordinate: FromRgb ignores it, and the colors ToRgba32 and ToRgba64 give are opaque.
• A color outside the gamut of the space is clipped component by component (CSS maps it into the gamut instead).
• Hsl, Hsv, Hwb and Cmyk describe the stored RGB values as they are, whatever their color space: they take no space. Cmyk does not describe what a press prints: to prepare colors for print, use an ICC conversion.

The white is D50

CieXyz is relative to CieXyz.D50 in every conversion, as the lab() colors of CSS and the connection space of ICC profiles are. CieLab.FromXyz and CieLuv.FromXyz take another white, and CieXyz.Adapt moves a color from a white to another with the Bradford transform. The conversions use the numbers of CSS Color 4, and are tested against its sample code.

Compare colors

ColorDifference measures how different two colors look:

With CIEDE2000, a difference of about 1 is the smallest one people notice.

Mix colors and change hues

Oklab.Lerp and Oklch.Lerp mix two colors, as the palette of the example above does. The hues of Oklch.Lerp follow the arc a HueInterpolation selects: Shorter (the default, as in CSS), Longer, Increasing or Decreasing.

Hues are in degrees, in [0, 360). A gray has no hue: when one of the colors is gray, Oklch.Lerp takes the hue of the other one.

Read and write CSS notations

Rgba32.ParseCss (and TryParseCss) reads a CSS color and converts it to sRGB: the hexadecimal notation, rgb(), rgba(), hsl(), hsla(), hwb(), lab(), lch(), oklab() and oklch(). Rgba32.ParseHex reads the hexadecimal notation only.

• Parse and TryParse of CieLab, CieLch, Oklab, Oklch, Hsl and Hwb read their own notation, with the modern syntax (/ alpha, none), and for hsl() the legacy syntax with commas too. The alpha is returned apart.
• Percentages, angles (deg, grad, rad, turn) and the clamping of CSS are applied as the specification does.
• ToCssString writes the modern syntax, with the shortest numbers that read back the same values.
• Named colors (red), calc(), relative colors and color() are not supported. The Colors class has the named colors of CSS as Rgba32 values.

The values of a color are sample values: drawn on an image, they are not converted to its color profile. See Color management.