Shader "SaberShad/GrayImageEffect"
{
    Properties
	{
		_MainTex ("Main Texture", 2D) = "white" {}
        // _RPath ("RPath", Range(0, 1)) = 0.2125
        // _GPath ("GPath", Range(0, 1)) = 0.7154 
        // _BPath ("BPath", Range(0, 1)) = 0.0721 
		// _GrayAmount("GrayAmount", Range(0, 1)) = 0.5
		_Contrast("Contrast", float) = 1//调整对比度
		_Saturation("Saturation", float) = 0.63//调整饱和度
		_Brightness("Brightness", float) = 0.72//调整亮度(明度)
		_Color ("Tint", Color) = (1,1,1,0)

		_StencilComp ("Stencil Comparison", Float) = 8
		_Stencil ("Stencil ID", Float) = 0
		_StencilOp ("Stencil Operation", Float) = 0
		_StencilWriteMask ("Stencil Write Mask", Float) = 255
		_StencilReadMask ("Stencil Read Mask", Float) = 255

		_ColorMask ("Color Mask", Float) = 15

		[Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0
	}

	SubShader
	{
		Tags
		{ 
			"Queue"="Transparent" 
			"IgnoreProjector"="True" 
			"RenderType"="Transparent" 
			"PreviewType"="Plane"
			"CanUseSpriteAtlas"="True"
		}

		Stencil
		{
			Ref [_Stencil]
			Comp [_StencilComp]
			Pass [_StencilOp] 
			ReadMask [_StencilReadMask]
			WriteMask [_StencilWriteMask]
		}

		Blend SrcAlpha OneMinusSrcAlpha
		Cull Off 
        ZWrite Off 
        ZTest Always

		ZTest [unity_GUIZTestMode]
		ColorMask [_ColorMask]

		Pass
		{
			Name "Default"
		CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#pragma target 2.0

			#include "UnityCG.cginc"
			#include "UnityUI.cginc"

			#pragma multi_compile __ UNITY_UI_ALPHACLIP
			
			struct appdata_t
			{
				float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
			};

			struct v2f
			{
				float4 vertex   : SV_POSITION;
                fixed4 color : COLOR;
                half2 texcoord  : TEXCOORD0;
			};
			
			fixed4 _Color;
			float4 _ClipRect;

			sampler2D _MainTex;
			float4 _MainTex_ST;
            // fixed _RPath, _GPath, _BPath;
			fixed _Contrast, _Saturation, _Brightness;
			v2f vert(appdata_t IN)
			{
				v2f OUT;
                OUT.vertex = UnityObjectToClipPos(IN.vertex);
                OUT.texcoord = IN.texcoord;
                #ifdef UNITY_HALF_TEXEL_OFFSET
                    OUT.vertex.xy += (_ScreenParams.zw-1.0) * float2(-1,1) * OUT.vertex.w;
                #endif 
                OUT.color = IN.color * _Color;
                return OUT;
			}

			fixed4 frag(v2f i) : SV_Target
			{
				fixed4 col = tex2D(_MainTex, i.texcoord);  
                //brigtness亮度
                fixed3 finalColor = col * _Brightness;  
                //saturation调整饱和度
                fixed gray = 0.2125 * col.r + 0.7154 * col.g + 0.0721 * col.b;  
                fixed3 grayColor = fixed3(gray, gray, gray);  
                finalColor = lerp(grayColor, finalColor, _Saturation);  
                //contrast调整对比度
                fixed3 avgColor = fixed3(0.5, 0.5, 0.5);    
                finalColor = lerp(avgColor, finalColor, _Contrast);  

                return fixed4(finalColor, col.a);  
			}
		ENDCG
		}
    }
}