graycoreio/daffodil

@use 'variables' as v;

// Calculate the luminance of a color.
// Luminance is defined as a decimal value between 0 and 1
// with "0" corresponding to "no brightness"
// and "1" corresponding to "full brightness".
//
// See https://www.w3.org/TR/WCAG20-TECHS/G17.html#G17-tests

@function daff-luminance($color) {
    $red-index: red($color) + 1;
    $green-index: green($color) + 1;
    $blue-index: blue($color) + 1;

    $red: nth(v.$linear-channel-values, $red-index);
    $green: nth(v.$linear-channel-values, $green-index);
    $blue: nth(v.$linear-channel-values, $blue-index);
    @return 0.2126 * $red + 0.7152 * $green + 0.0722 * $blue;
}