Javascript RGB ⇔ HSV

gistfile1.js

// Returns [hue, sat, val]. All 6 values are between 0...1.

function rgb2hsv(r, g, b) {
    var v =     Math.max(r, g, b),
        x = v - Math.min(r, g, b);
    return [
        (   x == 0 ?               0 :
            v == g ? (b - r) / x + 2 :
            v == b ? (r - g) / x + 4 :
                     (g - b) / x + 6
        ) % 6 / 6,
        v == 0 ? 0 : x / v,
        v
    ]
}

// Returns [red, green, blue]. All 6 values are between 0...1.

function hsv2rgb(h, s, v) {
    var c = v * s,
        h = h * 6,
        x = c * (1 - Math.abs(h % 2 - 1)),
        m = v - c,
        [r, g, b] =
            h < 1 ? [c, x, 0] :
            h < 2 ? [x, c, 0] :
            h < 3 ? [0, c, x] :
            h < 4 ? [0, x, c] :
            h < 5 ? [x, 0, c] :
                    [c, 0, x];
    return [r + m, g + m, b + m]
}