https://github.com/spenserblack/relative-luminance-rs

Get the relative luminance of a color
https://github.com/spenserblack/relative-luminance-rs

color contrast luminance luminosity theme

Last synced: 3 months ago
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Get the relative luminance of a color

• Host: GitHub
• URL: https://github.com/spenserblack/relative-luminance-rs
• Owner: spenserblack
• License: apache-2.0
• Created: 2025-01-08T20:34:00.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2025-05-14T13:43:16.000Z (about 1 year ago)
• Last Synced: 2025-10-08T13:48:25.884Z (8 months ago)
• Topics: color, contrast, luminance, luminosity, theme
• Language: Rust
• Homepage:
• Size: 17.6 KB
• Stars: 0
• Watchers: 1
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE-APACHE

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README

          
# relative-luminance

[![Crates.io Version](https://img.shields.io/crates/v/relative-luminance)](https://crates.io/crates/relative-luminance)

[![CI](https://github.com/spenserblack/relative-luminance-rs/actions/workflows/ci.yml/badge.svg)](https://github.com/spenserblack/relative-luminance-rs/actions/workflows/ci.yml)

This is a small crate that provides utilities to handle

[relative luminance][relative-luminance]. In short, among RGB color channels, green

represents the majority of light perceived by the typical human eye, then red, then

blue. This can explain why white text may be hard to read on a green (`#00FF00`)

background, yet black text can be hard to read on a blue (`#0000FF`) background.

| background | foreground | readability |

| :--------: | :--------: | :---------: |

| `#00FF00` | `#FFFFFF` | hard to read |

| `#00FF00` | `#000000` | readable |

| `#0000FF` | `#FFFFFF` | readable |

| `#0000FF` | `#000000` | hard to read |

Run `cargo run --example contrast` to see an example of how this looks.

## Example usage

```rust

use relative_luminance::*;

// Choose a foreground color that contrasts with the background color

let fg_color = if bg_color.relative_luminance() > 0.5 {

    dark_color

} else {

    light_color

};

println!("{}", "Hello, World!".color(fg_color).on_color(bg_color));

```

[relative-luminance]: https://en.wikipedia.org/wiki/Relative_luminance