Crate relative_luminance

This crate helps calculate relative luminance values for colors. This can help determine if a color looks light or dark, which may be different from if a color is mathematically light or dark. For example, even bright blue (#0000FF) can appear to be dark to many people.

Examples

use relative_luminance::{Luminance, Rgb};

let black: Rgb<f32> = Rgb { r: 0.0, g: 0.0, b: 0.0 };
let white: Rgb<f32> = Rgb { r: 1.0, g: 1.0, b: 1.0 };
let green: Rgb<f32> = Rgb { r: 0.0, g: 1.0, b: 0.0 };
let blue: Rgb<f32> = Rgb { r: 0.0, g: 0.0, b: 1.0 };

// If luminance is above 0.5, it can be considered bright.
assert_eq!(black.relative_luminance(), 0.0);
assert_eq!(white.relative_luminance(), 1.0);
assert!(green.relative_luminance() > 0.5);
assert!(blue.relative_luminance() < 0.5);

use relative_luminance::{Luminance, Rgb};

/// RGB channels in the range [0, 255].
struct MyRgb {
    r: u8,
    g: u8,
    b: u8,
}

impl Luminance<f32> for MyRgb {
    fn luminance_rgb(&self) -> Rgb<f32> {
        Rgb {
            // Normalizing color channels to the range [0.0, 1.0]
            r: f32::from(self.r) / 255.0,
            g: f32::from(self.g) / 255.0,
            b: f32::from(self.b) / 255.0,
        }
    }
}

let black = MyRgb { r: 0, g: 0, b: 0 };
let white = MyRgb { r: 255, g: 255, b: 255 };

assert_eq!(black.relative_luminance(), 0.0);
assert_eq!(white.relative_luminance(), 1.0);

Structs

Rgb

Struct for containing RGB channels that can be used for calculating luminance.

Traits

Luminance

Implement this trait on your color type to provide relative luminance calculations.

LuminanceValue

This trait is used to define numerical types that can be used to calculate relative luminance values.