relative-luminance

This is a small crate that provides utilities to handle 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

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));