Unity-NGUI灰度图设置

  关卡设计时，有些未解锁关卡需要设置为灰度图，NGUI中一般空间shader为：Transparent Colored，修改该shader即可（修改部分标记为红色）：

Shader "Unlit/Transparent Colored 4" {
	Properties
	{
		_MainTex ("Base (RGB), Alpha (A)", 2D) = "black" {}
	}
	
	SubShader
	{
		LOD 100

		Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Transparent"
		}
		
		Cull Off
		Lighting Off
		ZWrite Off
		Fog { Mode Off }
		Offset -1, -1
		Blend SrcAlpha OneMinusSrcAlpha

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
				
			#include "UnityCG.cginc"
	
			struct appdata_t
			{
				float4 vertex : POSITION;
				float2 texcoord : TEXCOORD0;
				fixed4 color : COLOR;
			};
	
			struct v2f
			{
				float4 vertex : SV_POSITION;
				half2 texcoord : TEXCOORD0;
				fixed4 color : COLOR;
			};
	
			sampler2D _MainTex;
			float4 _MainTex_ST;
				
			v2f vert (appdata_t v)
			{
				v2f o;
				o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
				o.texcoord = v.texcoord;
				o.color = v.color;
				return o;
			}
				
			fixed4 frag (v2f i) : COLOR
			{
				
//				fixed4 col = tex2D(_MainTex, i.texcoord) * i.color;
//				return col;
				fixed4 col;
				if(i.color.r==0 && i.color.g==0 && i.color.b==0){
					col = tex2D(_MainTex, i.texcoord);
					float grey = dot(col.rgb, float3(0.299, 0.587, 0.114));  
					col.rgb = float3(grey, grey, grey); 
				}else{
					col = tex2D(_MainTex, i.texcoord) * i.color;

				}
			

				return col;
			}
			ENDCG
		}
	}

	SubShader
	{
		LOD 100

		Tags
		{
			"Queue" = "Transparent"
			"IgnoreProjector" = "True"
			"RenderType" = "Transparent"
		}
		
		Pass
		{
			Cull Off
			Lighting Off
			ZWrite Off
			Fog { Mode Off }
			Offset -1, -1
			ColorMask RGB
			AlphaTest Greater .01
			Blend SrcAlpha OneMinusSrcAlpha
			ColorMaterial AmbientAndDiffuse
			
			SetTexture [_MainTex]
			{
				Combine Texture * Primary
			}
		}
	}
}

但是要注意，加上if判断句肯定有性能开销，使用时根据具体情况而定