flashrod

■AS3でRGBとHSBを相互変換する 22:13

HSBとRGBの相互変換はここにかいてあるとおり。

HSV色空間 - Wikipedia

        /** RGBからHSBをつくる
         * @param r 色の赤色成分(0〜255)
         * @param g 色の緑色成分(0〜255)
         * @param b 色の青色成分(0〜255)
         * @return HSB配列([0]=hue, [1]=saturation, [2]=brightness)
         */
        public static function RGBtoHSB(r:int, g:int, b:int):Array {
            var cmax:Number = Math.max(r, g, b);
            var cmin:Number = Math.min(r, g, b);
            var brightness:Number = cmax / 255.0;
            var hue:Number = 0;
            var saturation:Number = (cmax != 0) ? (cmax - cmin) / cmax : 0;
            if (saturation != 0) {
                var redc:Number = (cmax - r) / (cmax - cmin);
                var greenc:Number = (cmax - g) / (cmax - cmin);
                var bluec:Number = (cmax - b) / (cmax - cmin);
                if (r == cmax) {
                    hue = bluec - greenc;
                } else if (g == cmax) {
                    hue = 2.0 + redc - bluec;
                } else {
                    hue = 4.0 + greenc - redc;
                }
                hue = hue / 6.0;
                if (hue < 0) {
                    hue = hue + 1.0;
                }
            }
            return [hue, saturation, brightness];
        }

AS3のMath.max()やmin()は三つ以上指定できるので簡潔に書ける。

        /** HSBからRGBをつくる
         * @param hue 色の色相成分(小数部 * 360度が色相角度)
         * @param saturation 色の彩度(0.0 〜 1.0 の範囲の数)
         * @param brightness 色の明度(0.0 〜 1.0 の範囲の数)
         * @return RGBカラー
         */
        public static function HSBtoRGB(hue:Number, saturation:Number, brightness:Number):uint {
            var r:int = 0;
            var g:int = 0;
            var b:int = 0;
            if (saturation == 0) {
                r = g = b = brightness * 255.0 + 0.5;
            } else {
                var h:Number = (hue - Math.floor(hue)) * 6.0;
                var f:Number = h - Math.floor(h);
                var p:Number = brightness * (1.0 - saturation);
                var q:Number = brightness * (1.0 - saturation * f);
                var t:Number = brightness * (1.0 - (saturation * (1.0 - f)));
                switch (int(h)) {
                case 0:
                    r = brightness * 255.0 + 0.5;
                    g = t * 255.0 + 0.5;
                    b = p * 255.0 + 0.5;
                    break;
                case 1:
                    r = q * 255.0 + 0.5;
                    g = brightness * 255.0 + 0.5;
                    b = p * 255.0 + 0.5;
                    break;
                case 2:
                    r = p * 255.0 + 0.5;
                    g = brightness * 255.0 + 0.5;
                    b = t * 255.0 + 0.5;
                    break;
                case 3:
                    r = p * 255.0 + 0.5;
                    g = q * 255.0 + 0.5;
                    b = brightness * 255.0 + 0.5;
                    break;
                case 4:
                    r = t * 255.0 + 0.5;
                    g = p * 255.0 + 0.5;
                    b = brightness * 255.0 + 0.5;
                    break;
                case 5:
                    r = brightness * 255.0 + 0.5;
                    g = p * 255.0 + 0.5;
                    b = q * 255.0 + 0.5;
                    break;
                }
            }
            return (r << 16) | (g << 8) | (b << 0);
        }

Flashは半透明の重ね合わせなんかが簡単にできるのであまり需要はないかもしれない。