Shader "Custom/ScreenNoise"
{
    Properties
    {
        _MainTex ("Image", 2D) = "white" {}

        _Colour1 ("Colour 1", Color) = (0.0, 0.0, 0.0, 1.0)
        _Colour2 ("Colour 2", Color) = (1.0, 1.0, 1.0, 1.0)
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 200

        Pass {
            Cull Off

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

            sampler2D _MainTex;
            float4 _MainTex_ST;

            CBUFFER_START(UnityPerMaterial)
            uniform float4 _Colour1;
            uniform float4 _Colour2;
            CBUFFER_END

            struct Data
            {
                float4 vertex : POSITION;
            };

            struct V2F
            {
                float4 position : SV_POSITION;
                float4 screenuv : TEXCOORD0;
            };

            V2F vert(Data v)
            {
                V2F o;
                o.position = UnityObjectToClipPos(v.vertex);
                o.screenuv = ComputeScreenPos(o.position);
                return o;
            }

            fixed4 frag(V2F i) : SV_TARGET
            {
                half2 textureCoordinate = ((i.screenuv.xy / i.screenuv.w) % 1.0) * _MainTex_ST.xy;
                half coordoffset = (_MainTex_ST.zw * _Time) % 1.0;
                textureCoordinate.x += coordoffset;
                textureCoordinate.y += coordoffset;
                return lerp(_Colour1, _Colour2, tex2D(_MainTex, textureCoordinate).r);
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}