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terminal: add contrast function based on w3c

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This commit is contained in:
Mitchell Hashimoto
2023-08-30 10:18:18 -07:00
parent 0e8412ec19
commit fb2d4faa03
1 changed files with 17 additions and 0 deletions
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17
src/terminal/color.zig
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@ -103,6 +103,23 @@ pub const RGB = struct {
return self.r == other.r and self.g == other.g and self.b == other.b; return self.r == other.r and self.g == other.g and self.b == other.b;
} }
/// Calculates the contrast ratio between two colors. The contrast
/// ration is a value between 1 and 21 where 1 is the lowest contrast
/// and 21 is the highest contrast.
///
/// https://www.w3.org/TR/WCAG20/#contrast-ratiodef
pub fn contrast(self: RGB, other: RGB) f64 {
// pair[0] = lighter, pair[1] = darker
const pair: [2]f64 = pair: {
const self_lum = self.luminance();
const other_lum = other.luminance();
if (self_lum > other_lum) break :pair .{ self_lum, other_lum };
break :pair .{ other_lum, self_lum };
};
return (pair[0] + 0.05) / (pair[1] + 0.05);
}
/// Calculates luminance based on the W3C formula. This returns a /// Calculates luminance based on the W3C formula. This returns a
/// normalized value between 0 and 1 where 0 is black and 1 is white. /// normalized value between 0 and 1 where 0 is black and 1 is white.
/// ///