Unity Ugui Image置灰Shader，支持Mask裁剪

Shader "UI/ImageGreyShader"
{
    Properties
    {
        [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}
        _Color("Tint", Color) = (1,1,1,1)

		//MASK SUPPORT ADD
		_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
		//MASK SUPPORT END

    }

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


		//MASK SUPPORT ADD
		Stencil
		{
			Ref [_Stencil]
			Comp [_StencilComp]
			Pass [_StencilOp] 
			ReadMask [_StencilReadMask]
			WriteMask [_StencilWriteMask]
		}
		ColorMask [_ColorMask]
		//MASK SUPPORT END


	 // 源rgba*源a + 背景rgba*(1-源A值)   
        Blend SrcAlpha OneMinusSrcAlpha
       

        Pass
    {
        CGPROGRAM
		#pragma vertex vert     
		#pragma fragment frag     
		#include "UnityCG.cginc"     

        struct appdata_t
    {
        float4 vertex   : POSITION;
        float4 color    : COLOR;
        float2 texcoord : TEXCOORD0;
    };

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

    sampler2D _MainTex;
    fixed4 _Color;

    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);
#endif     
        OUT.color = IN.color * _Color;
        return OUT;
    }

    fixed4 frag(v2f IN) : SV_Target
    {
        half4 color = tex2D(_MainTex, IN.texcoord) * IN.color;
        float grey = dot(color.rgb, fixed3(0.22, 0.707, 0.071));
        return half4(grey,grey,grey,color.a);
    }
        ENDCG
    }
    }
}