RedOffsetShader.shader

Shader "Hidden/RedOffsetShader" {
  Properties {
    _MainTex ("Base (RGB)", 2D) = "white" {}
  }
  SubShader {
    Pass {
      CGPROGRAM
      #pragma vertex vert_img
      #pragma fragment frag

      #include "UnityCG.cginc"

      uniform sampler2D _MainTex;

      float4 frag(v2f_img i) : COLOR {
        half4 color = tex2D(_MainTex, i.uv);

        for (float y = -0.5; y <= 0; y += 0.025) {
          float2 offsetUv = float2(i.uv.x, i.uv.y + y);
          half4 offsetColor = tex2D(_MainTex, offsetUv);

          if (offsetColor.r > offsetColor.g &&
              offsetColor.r > offsetColor.b) {
            offsetColor.rgb = lerp(color.rgb, offsetColor.rgb, abs(0.5 + y));
            return offsetColor;
          }
        }

        return color;
      }
      ENDCG
    }
  }
}