HSV与RGB色彩模型互相转换

    HSV与RGB是ArcGIS中用的最多的两种色彩模型，这两种色彩模型基本信息就不做过多介绍了。下面是互相转换的代码

1、HSV转RGB 

     Arcgis Engine中可以将 Symbol中的Color先转为 IHsvColor这个接口，在这个接口中获取H、S、V三个值，我这里方便计算，将S、V值除以了100。

            IHsvColor pHsvColor = pSetFillSymbol.Color as IHsvColor;
            if(pHsvColor!=null&&pHsvColor.NullColor==false)
            {
                int H = pHsvColor.Hue;
                double S = Convert.ToDouble(pHsvColor.Saturation)/100;
                double V = Convert.ToDouble(pHsvColor.Value) / 100;
                Color pfill_Color = HSVToRGB(H,S,V);
                this.cPEFill.Color = pfill_Color;
            }

        /// 将HSV色彩模型转换为RGB模型
        /// </summary>
        /// <param name="H">色调 0-360</param>
        /// <param name="S">饱和度 0-1</param>
        /// <param name="V">亮度 0-1</param>
        /// <returns></returns>
        private Color HSVToRGB(int H,double S,double V)
        {
            if ((H >= 0 && H <= 360) && (S >= 0 && S <= 1) && (V >= 0 && V <= 1))
            {
                int R=0, G=0, B = 0;
                double _R=0, _G=0, _B = 0;
                var C = V * S;                
                var X = C * (1 - Math.Abs((H / 60)%2-1));
                var m = V - C;
                if (H >= 0 && H < 60)
                {
                    _R = C;
                    _G = X;
                    _B = 0;
                }
                else if(H >= 60 && H < 120)
                {
                    _R = X;
                    _G = C;
                    _B = 0;
                }
                else if(H > 120 && H <180)
                {
                    _R = 0;
                    _G = C;
                    _B = X;
                }
                else if(H >= 180 && H < 240)
                {
                    _R = 0;
                    _G = X;
                    _B = C;
                }
                else if(H >= 240 && H < 300)
                {
                    _R = X;
                    _G = 0;
                    _B = C;
                }
                else if (H >= 300 && H < 360)
                {
                    _R = C;
                    _G = 0;
                    _B = X;
                }
                 R = Convert.ToInt32((_R + m) * 255);
                 G = Convert.ToInt32((_G + m) * 255);
                 B = Convert.ToInt32((_B + m) * 255);

                return Color.FromArgb(R, G, B);
            }
            else
            {
                return Color.FromArgb(0, 0, 0);
            }
        }

2、RGB转HSV

/// <summary>
        /// 将RGB色彩模型转换为HSV色彩模型
        /// </summary>
        /// <param name="R">0-255</param>
        /// <param name="G">0-255</param>
        /// <param name="B">0-255</param>
        /// <returns></returns>
        private IHsvColor RGBToHSV(int R,int G,int B)
        {
            double _R = 0, _G = 0, _B = 0;
            _R = Convert.ToDouble(R) / 255;
            _G = Convert.ToDouble(G) / 255;
            _B = Convert.ToDouble(B) / 255;
            double[] _RGB = new double[] {_R,_G,_B };
            var C_max = _RGB.Max();
            var C_min = _RGB.Min();
            var D_value = C_max - C_min;
            double H = 0, S = 0, V = 0;
            if(D_value==0)
            {
                H = 0;
            }
            else if(C_max==_R)
            {
                H = (((_G - _B) / D_value) % 6) * 60;
            }
            else if(C_max==_G)
            {
                H = (((_B - _R) / D_value) + 2) * 60;
            }
            else if(C_max==_B)
            {
                H = (((_R - _G) / D_value) + 4) * 60;
            }

            if (C_max == 0)
            {
                S = 0;
            }
            else
            {
                S = D_value / C_max;
            }
            V = C_max;

            IHsvColor pHsvColor = new HsvColorClass();
            pHsvColor.Hue = Convert.ToInt32(H);
            pHsvColor.Saturation = Convert.ToInt32(S*100);
            pHsvColor.Value = Convert.ToInt32(V*100);
            return pHsvColor;
        }