裁剪图片，调整Radius，方形-圆形


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//裁剪图片，调整Radius，方形-圆形
Shader "Self/Circular"
{
Properties
{
_MainTex ("Base (RGB), Alpha (A)", 2D) = "white" {}

    _StencilComp ("Stencil Comparison", Float) = 8
    _Stencil ("Stencil ID", Float) = 0
    _StencilOp ("Stencil Operation", Float) = 0
    _StencilWriteMask ("Stencil Write Mask", Float) = 255
    _StencilReadMask ("Stencil Read Mask", Float) = 255

    _ColorMask ("Color Mask", Float) = 15
    // 以 1 - _Radius 长度为半径的圆形
    _Radius ("Radius", Range(0,0.5)) = 0.5
}

SubShader
{
    LOD 100

    Tags
    {
        "Queue" = "Transparent"
        "IgnoreProjector" = "True"
        "RenderType" = "Transparent"
        "PreviewType"="Plane"
    }

    Stencil
    {
        Ref [_Stencil]
        Comp [_StencilComp]
        Pass [_StencilOp] 
        ReadMask [_StencilReadMask]
        WriteMask [_StencilWriteMask]
    }
    
    Cull Off
    Lighting Off
    ZWrite Off
    ZTest [unity_GUIZTestMode]
    Offset -1, -1
    Fog { Mode Off }
    Blend SrcAlpha OneMinusSrcAlpha
    ColorMask [_ColorMask]

    

    Pass
    {
        CGPROGRAM
            #pragma target 3.0
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            float _Radius;

            struct appdata_t
            {
                float4 vertex : POSITION;
                float2 texcoord : TEXCOORD0;
                fixed4 color : COLOR;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                half2 texcoord : TEXCOORD0;
                fixed4 color : COLOR;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            
            v2f vert (appdata_t v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
                o.color = v.color;

ifdef UNITY_HALF_TEXEL_OFFSET

                o.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);

endif

                return o;
            }
            
            fixed4 frag (v2f i) : COLOR
            {
                float2 uv = i.texcoord.xy;
                float4 c = i.color;
                // 左下四方块
                if(uv.x < _Radius && uv.y < _Radius)
                {
                    float2 r;
                    r.x = uv.x - _Radius;
                    r.y = uv.y - _Radius;
                    float rr = length(r);
                    // 裁剪
                    if(rr > _Radius)
                    {
                        c.a = 0;
                    }
                }
                // 左上四方块
                else if(uv.x < _Radius && uv.y > 1- _Radius)
                {
                    float2 r;
                    r.x = uv.x - _Radius;
                    r.y = uv.y + _Radius - 1;
                    float rr = length(r);
                    // 裁剪
                    if(rr > _Radius)
                    {
                        c.a = 0;
                    }   
                }
                // 右下四方块
                else if(uv.x > 1 - _Radius && uv.y < _Radius)
                {
                    float2 r;
                    r.x = uv.x + _Radius - 1;
                    r.y = uv.y - _Radius;
                    float rr = length(r);
                    // 裁剪
                    if(rr > _Radius)
                    {
                        c.a = 0;
                    }   
                }
                // 右上四方块
                else if(uv.x > 1 - _Radius && uv.y > 1- _Radius)
                {
                    float2 r;
                    r.x = uv.x + _Radius - 1;
                    r.y = uv.y + _Radius - 1;
                    float rr = length(r);
                    // 裁剪
                    if(rr > _Radius)
                    {
                        c.a = 0;
                    }   
                }                                   
                
                fixed4 col = tex2D(_MainTex, i.texcoord) * c;
                clip (col.a - 0.01);
                return col;
            }
                            
        ENDCG
    }
}

}
}