Shader "Hidden/test"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Cull Off ZWrite Off ZTest Always
        Tags { "Queue" = "Transparent" }
        Pass//---------------------------渲染图片边框-----------------------------
        {
            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;
            fixed4 _MainTex_ST;
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
            fixed4 frag (v2f i) : SV_Target
            {
                // 白色
                fixed4 col = fixed4(1,0,0,1);
                return col;
            }
            ENDCG
        }
    }
}

Shader "Custom/OutLineShader"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _OutLineWidth("OutLineWidth",Range(0,5)) = 0.1
        _OutLineColor("OutLineColor",Color)=(1,1,1,1)
    }
    SubShader
    {
        Tags{
            "Queue" = "Geometry-20"
        }
        // 关闭剔除，让双面都能显示
        Cull off
        // 开启混合
        Blend SrcAlpha OneMinusSrcAlpha
        Pass
        {
            // 关闭深度测试，使用Queue=Geometry-20的队列(用于2D游戏)
            ZWrite off
            CGPROGRAM
            #include "UnityCG.cginc"
            #pragma vertex vert
            #pragma fragment frag

            struct inputV
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };
            struct outputV
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
             };
             sampler2D _MainTex;
             float4 _MainTex_TexelSize;
             float _OutLineWidth;
             float3 _OutLineColor;
            outputV vert(inputV v)
            {
                outputV o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            fixed4 frag(outputV i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                float2 uv_up = i.uv + _MainTex_TexelSize.xy * float2(0,1) * _OutLineWidth;
                float2 uv_down = i.uv + _MainTex_TexelSize.xy * float2(0,-1) * _OutLineWidth;
                float2 uv_left = i.uv + _MainTex_TexelSize.xy * float2(-1,0) * _OutLineWidth;
                float2 uv_right = i.uv + _MainTex_TexelSize.xy * float2(1,0) * _OutLineWidth;
                
                float w =  tex2D(_MainTex, uv_up).a * tex2D(_MainTex, uv_down).a * tex2D(_MainTex, uv_left).a * tex2D(_MainTex, uv_right).a;
                // 描边
                col.rgb = lerp(_OutLineColor.rgb,col.rgb,w);
                return col;
            }
            ENDCG
        }

    }
}

Shader "Hidden/test"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _BorderColor("BorderColor",Color)=(1,0,0,1)
        _Offset("Offset",Range(0,1)) = 0.05
    }
    SubShader
    {
        Cull Off ZWrite Off
        Tags { "Queue" = "Transparent" }
        // 混合
        Blend SrcAlpha OneMinusSrcAlpha
        pass//----------------------渲染上边缘------------------------
        {
            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;
            fixed4 _MainTex_ST;
            fixed4 _BorderColor;
            float _Offset;
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.vertex.y += _Offset;
                o.uv = v.uv;
                return o;
            }
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = _BorderColor*tex2D(_MainTex, i.uv).a;
                return col;
            }
            ENDCG
        }
        pass//----------------------渲染右边缘------------------------
        {
			...
        }
        pass//---------------------渲染下边缘-------------------------
        {
			...
        }
        pass//---------------------渲染左边缘-------------------------
        {
			...
        }
        pass//------------------渲染模型本身----------------------------
        {
            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;
            fixed4 _MainTex_ST;
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                return col;
            }
            ENDCG
        }
    }
}

Shader "Hidden/test"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _BiggerBorder("BiggerBorder",Range(0,1)) = 0.5
        _Offset("Offset",Range(0,1)) = 0.05
    }
    SubShader
    {
        Cull Off ZWrite Off
        Tags { "Queue" = "Transparent" }
        Pass//---------------------------渲染图片边框-----------------------------
        {
            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;
            fixed4 _MainTex_ST;
            float _Offset;
            float _BiggerBorder;
            v2f vert (appdata v)
            {
                v2f o;
                // 顶点向外偏移，不是向上偏移
                v.vertex.xy += normalize(v.vertex.xy) * _BiggerBorder;
                o.vertex = UnityObjectToClipPos(v.vertex);
                // 重采样uv
                // o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.uv = v.uv;
                return o;
            }
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                if(col.a > 0.5)
                {
                    return col;
                }
                else        // 透明像素边界判断
                {
                    fixed4 up = tex2D(_MainTex, i.uv + float2(0, _Offset));
                    fixed4 down = tex2D(_MainTex, i.uv - float2(0, _Offset));
                    fixed4 left = tex2D(_MainTex, i.uv - float2(_Offset, 0));
                    fixed4 right = tex2D(_MainTex, i.uv + float2(_Offset, 0));
                    if(up.a > 0.5 || down.a > 0.5 || left.a > 0.5 || right.a > 0.5)
                    {
                        return fixed4(1,0,0,1);
                    }
                    discard;
                    return fixed4(0,0,0,0);
                }
            }
            ENDCG
        }
    }
}