使用纹理制作特效 - Photoshop色阶效果

Shader "PhotoshopLevels"
{
    Properties
    {
        _MainTex("MainTex", 2D) = "" {}

        _InBlack("InBlack", Range(0, 255)) = 0
        _InGamma("InGamma", Range(0, 255)) = 1.61
        _InWhite("InWhite", Range(0, 255)) = 255
        _OutBalck("OutBlack", Range(0, 255)) = 0
        _OutWhite("OutWhite", Range(0, 255)) = 255
    }

    SubShader
    {
        Tags
        {
            "RenderType" = "Opaque"
        }

        LOD 200

        CGPROGRAM

        #pragma surface surf Lambert

        sampler2D _MainTex;

        float _InBlack;
        float _InGamma;
        float _InWhite;
        float _OutBlack;
        float _OutWhite;

        float outRPixel;

        struct Input
        {
            float2 uv_MainTex;
        };

        void surf(Input IN, inout SurfaceOutput o)
        {
            float4 c = tex2D(_MainTex, IN.uv_MainTex);

            outRPixel = c.r * 255.0;

            outRPixel = max(0, outRPixel - _InBlack);

            outRPixel = saturate(pow(outRPixel / (_InWhite - _InBlack), _InGamma));

            outRPixel = (outRPixel * (_OutWhite - _OutBlack) + _OutBlack) / 255.0;

            c.r = outRPixel;

            o.Albedo = c.rgb;
            o.Alpha = c.a;
        }

        ENDCG
    }
}