Unity Image 马赛克效果Shader

效果图如下  貌似没有了透明通道

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Unlit/MaSaiKe"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_TillSize("Till Size",Range(0.001,0.05))=0.005
	}
	SubShader
	{
		Pass{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"

			struct a2v{
				float4 vertex:POSITION;
				float2 texcoord:TEXCOORD0;
			};
			struct v2f{
				float4 pos:POSITION;
				float2 uv:TEXCOORD0;
			};

			sampler2D _MainTex;
			float _TillSize;

			v2f vert(a2v v){
				v2f o;
				o.pos=UnityObjectToClipPos(v.vertex);
				o.uv=v.texcoord;
				return o;
			}

			fixed4 frag(v2f i):SV_Target{
				i.uv.x = floor(i.uv.x/_TillSize) * _TillSize;
				i.uv.y = floor(i.uv.y/_TillSize) * _TillSize;

				fixed4 col = tex2D(_MainTex,i.uv);
				return col;
			}

			ENDCG
		}			
	}
}