ReversedColor.shader

Shader "UI/Unlit/ReversedColor"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
    }
 
    SubShader
    {
        Tags { "RenderType"="Opaque" "Queue"="Transparent" }

        GrabPass { "_GrabTexture" }

        LOD 100
     
        Blend SrcAlpha OneMinusSrcAlpha

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

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
                float4 grabUV : TEXCOORD1;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            sampler2D _GrabTexture;
         
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                o.grabUV = ComputeGrabScreenPos(UnityObjectToClipPos(v.vertex));
                
                return o;
            }
         
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 grabCol = 1 - tex2D(_GrabTexture, i.grabUV);

                grabCol.a = col.a;

                return grabCol;
            }
            ENDCG
        }
    }
}