Unity Shader 边缘检测

边缘检测的原理是利用一些边缘检测算子对图像进行卷积操作，大家在很多场景中需要使用到，为此下面就给大家介绍下边缘检测的shader代码实现。

效果：

shader代码：

Shader "Custom/ScannerShader"
｛
    Properties
    ｛
        _MainTex ("Texture", 2D) = "white" ｛｝
        _MaskTex("MaskTex", 2D) = "white" ｛｝
        _EdgeOnly ("Edge Only", Float) = 1.0
        _EdgeColor ("Edgge Color", Color) = (0,0,0,1)
        _BackgroundColor ("Background Color",Color) = (1,1,1,0)
        _Thickness ("Thickness",Float) = 1.0
        _Speed("Speed",Range(-1,0))=-0.5
    ｝
    SubShader
    ｛
        Tags ｛ "RenderType"="Opaque" ｝
        cull off
        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;
            ｝;
            sampler2D _MainTex;
            float4 _MainTex_ST;
            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);
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            ｝
            ENDCG
        ｝
        Pass
        ｛
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            struct appdata
            ｛
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            ｝;
            struct v2f
            ｛                    
                float2 maskuv : TEXCOORD0;
                float2 uv[9] : TEXCOORD1;
                float4 vertex : SV_POSITION;
            ｝;
            sampler2D _MainTex;
            sampler2D _MaskTex;
            half4 _MainTex_TexelSize;
            fixed _EdgeOnly;
            fixed4 _EdgeColor;
            fixed4 _BackgroundColor;
            fixed _Thickness;
            fixed _Speed;
            fixed luminance(fixed4 color)
            ｛
                return 0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b;
            ｝
            half Sobel(v2f i)
            ｛
                const half Gx[9] = ｛-1,-2,-1,0,0,0,1,2,1｝;
                const half Gy[9] = ｛ -1,0,1,-2,0,2,-1,0,1 ｝;
                half texColor;
                half edgeX = 0;
                half edgeY = 0;
                for (int it = 0; it < 9; it++)
                ｛
                    texColor = luminance(tex2D(_MainTex, i.uv[it]));
                    edgeX += texColor * Gx[it];
                    edgeY += texColor * Gy[it];
                ｝
                half edge = 1 - abs(edgeX) - abs(edgeY);
                return edge;
            ｝
            v2f vert (appdata v)
            ｛
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                half2 uv = v.uv;
                o.maskuv = v.uv + frac(fixed2(0,_Speed * _Time.y));
                //o.maskuv = v.uv + fixed2(0.7 * _Time.y,0);
                o.uv[0] = uv + _MainTex_TexelSize.xy * half2(-1, -1) * _Thickness;
                o.uv[1] = uv + _MainTex_TexelSize.xy * half2(0, -1)* _Thickness;
                o.uv[2] = uv + _MainTex_TexelSize.xy * half2(1, -1)* _Thickness;
                o.uv[3] = uv + _MainTex_TexelSize.xy * half2(-1, 0)* _Thickness;
                o.uv[4] = uv + _MainTex_TexelSize.xy * half2(0, 0)* _Thickness;
                o.uv[5] = uv + _MainTex_TexelSize.xy * half2(1, 0)* _Thickness;
                o.uv[6] = uv + _MainTex_TexelSize.xy * half2(-1, 1)* _Thickness;
                o.uv[7] = uv + _MainTex_TexelSize.xy * half2(0, 1)* _Thickness;
                o.uv[8] = uv + _MainTex_TexelSize.xy * half2(1, 1)* _Thickness;
                return o;
            ｝
            fixed4 frag (v2f i) : SV_Target
            ｛
                half edge = Sobel(i);
                fixed4 maskColor = tex2D(_MaskTex, i.maskuv);
                fixed4 withEdgeColor = lerp(_EdgeColor,tex2D(_MainTex, i.uv[4]),edge);
                fixed4 onlyEdgeColor = lerp(_EdgeColor, _BackgroundColor, edge);
                fixed4 col = lerp(withEdgeColor, onlyEdgeColor, _EdgeOnly);
                return fixed4(col.rgb,col.a * (1.0 - maskColor.r));
            ｝
            ENDCG
        ｝
    ｝
｝