# .toXYZ()

Get a color's CIE XYZ values, where y is the relative luminance contrast is built on.

Get a color's CIE XYZ values with `toXYZ()`, the space the other color spaces are defined from. It takes nothing and returns an `XYZColor`, whose `y` is the color's relative luminance:

```swift
Color(hex: "#00B386").toXYZ()   // XYZColor(x: 0.204, y: 0.340, z: 0.280)
```

## Relative luminance

`y` runs from 0 for black to 1 for white, and it's the number WCAG contrast is built on. To check a pair of colors, use [`contrastRatio(to:method:)`](https://colortokenskit.com/api/contrast-ratio/index.md), which does the math for you.

## Converting onward

XYZ is a step between spaces: from an `XYZColor` you can go to `toRGB()`, `toLAB()` and `toLCH()`. It has no `toColor()`, so go through RGB or LCH to draw it, as in `xyz.toLCH().toColor()`.

## How it behaves

The white point is D65. Inside sRGB, `x` runs from 0 to 0.95, `y` from 0 to 1 and `z` from 0 to 1.09; conversions pass through extended sRGB without clipping, so Display P3 colors reach further. A token gives its light-mode value on iOS 17, macOS 14 and later. `lerp(_:t:)` mixes two `XYZColor` values in a straight line.

## API

```swift
public extension Color {
    func toXYZ() -> XYZColor
}

public struct XYZColor: Hashable, Sendable {
    public let x: CGFloat       // 0 to 0.95 inside sRGB
    public let y: CGFloat       // 0 to 1, relative luminance
    public let z: CGFloat       // 0 to 1.09 inside sRGB
    public let alpha: CGFloat   // 0 to 1

    public init(x: CGFloat, y: CGFloat, z: CGFloat, alpha: CGFloat)

    public func lerp(_ other: XYZColor, t: CGFloat) -> XYZColor
    public func toRGB() -> RGBColor
    public func toLAB() -> LABColor
    public func toLCH() -> LCHColor
}
```

`toXYZ()` takes no parameters.

## Sources

- [Color+ColorSpaces.swift](https://github.com/metasidd/ColorTokensKit-Swift/blob/main/Sources/ColorTokensKit/Platform/SwiftUI/Color+ColorSpaces.swift), which defines `toXYZ()` on `Color`.
- The [XYZ](https://github.com/metasidd/ColorTokensKit-Swift/tree/main/Sources/ColorTokensKit/ColorSpace/XYZ) folder, which defines `XYZColor`.
- W3C, [Web Content Accessibility Guidelines (WCAG) 2.2](https://www.w3.org/TR/WCAG22/), which defines relative luminance.

## See also

- [.contrastRatio(to:method:)](https://colortokenskit.com/api/contrast-ratio/index.md): Check WCAG 2 and APCA contrast in Swift, and keep your color pairs passing with a unit test.
- [.toLAB()](https://colortokenskit.com/api/to-lab/index.md): Change a color's lightness alone in CIELab, the lightness that decides contrast.
- [.toRGB()](https://colortokenskit.com/api/to-rgb/index.md): Read a color's red, green and blue channels, even past sRGB, to hand to other graphics code.
- [Glossary of color terms](https://colortokenskit.com/reference/glossary/index.md): Look up any color term on this site in plain words, from stop and token to chroma and gamut.

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From ColorTokensKit, by Penguin Design Ventures: https://colortokenskit.com/api/to-xyz/ (updated September 26, 2026).