/**
 * @preserve
 * Copyright 2015-2016 Igor Bezkrovnyi
 * All rights reserved. (MIT Licensed)
 *
 * rgb2hsl.ts - part of Image Quantization Library
 */
import { min3, max3 } from "../utils/arithmetic"

/**
 * Calculate HSL from RGB
 * Hue is in degrees [0..360]
 * Lightness: [0..1]
 * Saturation: [0..1]
 * http://web.archive.org/web/20060914040436/http://local.wasp.uwa.edu.au/~pbourke/colour/hsl/
 */
export function rgb2hsl(r : number, g : number, b : number) : {h : number; s : number; l : number} {
    const min   = min3(r, g, b),
          max   = max3(r, g, b),
          delta = max - min,
          l     = (min + max) / 510;

    let s = 0;
    if (l > 0 && l < 1) s = delta / (l < 0.5 ? (max + min) : (510 - max - min));

    let h = 0;
    if (delta > 0) {
        if (max === r) {
            h = (g - b) / delta;
        } else if (max === g) {
            h = (2 + (b - r) / delta);
        } else {
            h = (4 + (r - g) / delta);
        }

        h *= 60;
        if (h < 0) h += 360;
    }
    return { h, s, l };
}