toHsvString: function() {
            var hsv = rgbToHsv(this._r, this._g, this._b);
            var h = mathRound(hsv.h * 360), s = mathRound(hsv.s * 100), v = mathRound(hsv.v * 100);
            return (this._a == 1) ?
              "hsv("  + h + ", " + s + "%, " + v + "%)" :