Unity中的Shader(HSV,RGB转换)

//RGB转换：http://www.easyrgb.com/en/math.php#text22
Shader "HSVShader/ColorGradation_HSV" {
    Properties {
        //贴图
        _MainTex ("MainTex (RGB)", 2D) = "white" {}
        //Hue的值范围为0-359. 其他两个为0-1 ,这里我们设置到3，因为乘以3后 都不一定能到超过.
        _Hue ("Hue", Range(0,359)) = 0
        _Saturation ("Saturation", Range(0,3.0)) = 1.0
        _Value ("Value", Range(0,3.0)) = 1.0
    }
    SubShader {
    Pass {
        Tags { "RenderType"="Opaque" }
        LOD 200

        Lighting Off

        CGPROGRAM
        #pragma vertex vert_img
        #pragma fragment frag
        #include "UnityCG.cginc"


        sampler2D _MainTex;
        half _Hue;
        half _Saturation;
        half _Value;

        struct Input {
            float2 uv_MainTex;
        };

        //RGB to HSV
        float3 RGBConvertToHSV(float3 rgb)
        {
            float R = rgb.x/255,G = rgb.y/255,B = rgb.z/255;
            float3 hsv;
            float max1=max(R,max(G,B));
            float min1=min(R,min(G,B));
			float del_max = max1 - min1;
			hsv.z = max1;
			if (del_max == 0)
			{
				hsv.x = 0;
				hsv.y = 0;
			}
			else
			{
				hsv.y = del_max / max1;
				float del_R = (((max1 - R) / 6) + (del_max / 2)) / del_max;
				float del_G = (((max1 - G) / 6) + (del_max / 2)) / del_max;
				float del_B = (((max1 - B) / 6) + (del_max / 2)) / del_max;
				if (R == max1)hsv.x = del_B - del_G;
				else if (G == max1)hsv.x = (1 / 3) + del_R - del_B;
				else if (B == max1)hsv.x = (2 / 3) + del_G - del_R;
				if (hsv.x < 0)hsv.x += 1;
				if (hsv.x > 1)hsv.x -= 1;
			}
            /*if (R == max1) 
            {
                hsv.x = (G-B)/(max1-min1);
            }
            if (G == max1) 
            {
                hsv.x = 2 + (B-R)/(max1-min1);
                }
            if (B == max1) 
            {
                hsv.x = 4 + (R-G)/(max1-min1);
                }
            hsv.x = hsv.x * 60.0;   
            if (hsv.x < 0) 
                hsv.x = hsv.x + 360;
            hsv.z=max1;
            hsv.y=(max1-min1)/max1;*/
            return hsv;
        }

        //HSV to RGB
        float3 HSVConvertToRGB(float3 hsv)
        {
            float R,G,B;
            //float3 rgb;
            if( hsv.y == 0 )
            {
                /*R=G=B=hsv.z;*/
				R = hsv.z * 255;
				G = hsv.z * 255;
				B = hsv.z * 255;
            }
			else
			{
				float var_r, var_g, var_b;
				float var_h = hsv.x * 6;
				if (var_h == 6)var_h = 0;
				int var_i = (int)var_h;//把var_h转化为整数var_i；
				float var_1 = hsv.z*(1 - hsv.y);
				float var_2 = hsv.z*(1 - hsv.y*(var_h - var_i));
				float var_3 = hsv.z*(1 - hsv.y*(1 - (var_h - var_i)));
				if (var_i == 0) { var_r = hsv.z; var_g = var_3; var_b = var_1; }
				else if (var_i == 1) { var_r = var_2; var_g = hsv.z; var_b = var_1; }
				else if (var_i == 2) { var_r = var_1; var_g = hsv.z; var_b = var_3; }
				else if (var_i == 3) { var_r = var_1; var_g = var_2; var_b = hsv.z; }
				else if (var_i == 4) { var_r = var_3; var_g = var_1; var_b = hsv.z; }
				else { var_r = hsv.z; var_g = var_1; var_b = var_2; }

				R = var_r * 255;
				G = var_g * 255;
				B = var_b * 255;
			}
            /*else
            {
                hsv.x = hsv.x/60.0; 
                int i = (int)hsv.x;
                float f = hsv.x - (float)i;
                float a = hsv.z * ( 1 - hsv.y );
                float b = hsv.z * ( 1 - hsv.y * f );
                float c = hsv.z * ( 1 - hsv.y * (1 - f ) );
                switch(i)
                {
                    case 0: R = hsv.z; G = c; B = a;
                        break;
                    case 1: R = b; G = hsv.z; B = a; 
                        break;
                    case 2: R = a; G = hsv.z; B = c; 
                        break;
                    case 3: R = a; G = b; B = hsv.z; 
                        break;
                    case 4: R = c; G = a; B = hsv.z; 
                        break;
                    default: R = hsv.z; G = a; B = b; 
                        break;
                }
            }*/
            return float3(R,G,B);
        }       

        fixed4 frag (v2f_img i) : SV_Target
        {
            fixed4 original = tex2D(_MainTex, i.uv);    //获取贴图原始颜色

            float3 colorHSV;    
            colorHSV.xyz = RGBConvertToHSV(original.xyz);   //转换为HSV
            colorHSV.x += _Hue; //调整偏移Hue值
            colorHSV.x = colorHSV.x%360;    //超过360的值从0开始

            colorHSV.y *= _Saturation;  //调整饱和度
            colorHSV.z *= _Value;                           

            original.xyz = HSVConvertToRGB(colorHSV.xyz);   //将调整后的HSV，转换为RGB颜色

            return original;
        }
        ENDCG
    } 
    }
    FallBack "Diffuse"
}