Shader "MyShader/EasyImageEffectShader"
{
    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
        _Brightness("Brightness", Range(0,10)) = 1
        _Saturation("Saturation", Range(0,10)) = 1
        _Contrast("Contrast", Range(0,10)) = 1
    }
        SubShader
        {
            Tags { "RenderType" = "Opaque" }
            LOD 100

            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;
                };

                sampler2D _MainTex;
                float4 _MainTex_ST;

                fixed _Brightness;
                fixed _Saturation;
                fixed _Contrast;

                v2f vert(appdata v)
                {
                    v2f o;
                    o.vertex = UnityObjectToClipPos(v.vertex);
                    o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                    return o;
                }

                fixed4 frag(v2f i) : SV_Target
                {
                    fixed4 col = tex2D(_MainTex, i.uv);
                //brigtness亮度
                fixed3 finalColor = col * _Brightness;
                //saturation调整饱和度
                fixed gray = 0.2125 * col.r + 0.7154 * col.g + 0.0721 * col.b;
                fixed3 grayColor = fixed3(gray, gray, gray);
                finalColor = lerp(grayColor, finalColor, _Saturation);
                //contrast调整对比度
                fixed3 avgColor = fixed3(0.5, 0.5, 0.5);
                finalColor = lerp(avgColor, finalColor, _Contrast);
                return fixed4(finalColor, col.a);
            }
            ENDCG
        }
        }
}