Unity Sprite 灰色图

https://gameinstitute.qq.com/community/detail/122856

Sprite怎么变成灰色图效果，最简单的方法就是通过修改shader实现。

Shader "Sprite/SpriteGray"  
{
    Properties  
    {
    [PerRendererData] _MainTex("Sprite Texture", 2D) = "white" {}  
    _Color("Tint", Color) = (1, 1, 1, 1)  
        [MaterialToggle] PixelSnap("Pixel snap", Float) = 0  
    }  
    SubShader  
    {  
        Tags  
        {  
        "Queue" = "Transparent"  
        "IgnoreProjector" = "True"  
        "RenderType" = "Transparent"  
        "PreviewType" = "Plane"  
        "CanUseSpriteAtlas" = "True"  
    }  
        Cull Off  
            Lighting Off  
            ZWrite Off  
            Fog{ Mode Off }  
        Blend One OneMinusSrcAlpha  
            Pass  
        {  
            CGPROGRAM  
#pragma vertex vert  
#pragma fragment frag  
#pragma multi_compile DUMMY PIXELSNAP_ON  
#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;  
            };  
            fixed4 _Color;  
            v2f vert(appdata_t IN)  
            {  
                v2f OUT;  
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);  
                OUT.texcoord = IN.texcoord;  
                OUT.color = IN.color * _Color;  
#ifdef PIXELSNAP_ON  
                OUT.vertex = UnityPixelSnap(OUT.vertex);  
#endif  
                return OUT;  
            }  
            sampler2D _MainTex;  
            fixed4 frag(v2f IN) : SV_Target  
            {  
                fixed4 c = tex2D(_MainTex, IN.texcoord) * IN.color;  
                c.xyz *= c.a;//不加这个，alpha值低的时候，白色会消失看不见。  
                float gray = dot(c.xyz, float3(0.299, 0.587, 0.114));  
                //float gray = dot(c.xyz, float3(0.333, 0.333, 0.334));  
                c.xyz = float3(gray, gray, gray);  
                return c;  
            }  
            ENDCG  
        }  
    }  
}