Shader Texture中指定具体颜色进行高亮显示

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实现： 高亮一张texture上相同颜色的色块。<br>原理：使用step进行rgb的对比即可。<br><br><br><br>Shader "Unlit/ChooseContinent" {   //2018年4月8日     //for ui地图高亮所有相同的颜色块           Properties     {         _MainTex("Texture", 2D) = "white" {}         _SwitchColor("SwitchColor",Int) = 0 //高光还是直接返回         _HighlightColor("HighlightColor",Color) = (0.498,1,0,0.3)//高光颜色         _ChooseR("ChooseR",Int) = 255//点击选择的颜色值         _ChooseG("ChooseG",Int) = 255         _ChooseB("ChooseB",Int) = 255         _ThresholdValue("ThresholdValue",Int) = 10//判断范围的阀值         _VertexOffset("VertexOffset",Vector) = (5,-15,0,0)//顶点偏移     }           SubShader         {             Tags         {             "Queue" = "Transparent"             "IgnoreProjector" = "True"             "RenderType" = "Transparent"             "PreviewType" = "Plane"             "CanUseSpriteAtlas" = "True"         }                 Cull Back             Lighting Off             ZWrite Off             ZTest Off             Blend SrcAlpha OneMinusSrcAlpha                         Pass         {             Name "Default"             CGPROGRAM     #pragma vertex vert     #pragma fragment frag     #pragma target 2.0         #include "UnityCG.cginc"     #include "UnityUI.cginc"            struct appdata_t         {             float4 vertex   : POSITION;             float4 color    : COLOR;             float2 texcoord : TEXCOORD0;             UNITY_VERTEX_INPUT_INSTANCE_ID         };           struct v2f         {             float4 vertex   : SV_POSITION;             fixed4 color : COLOR;             float2 texcoord  : TEXCOORD0;             float4 worldPosition : TEXCOORD1;             UNITY_VERTEX_OUTPUT_STEREO         };           float4 _VertexOffset;         v2f vert(appdata_t IN)         {             v2f OUT;             UNITY_SETUP_INSTANCE_ID(IN);             UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);             OUT.worldPosition = IN.vertex;             OUT.vertex = UnityObjectToClipPos(OUT.worldPosition) - _VertexOffset;             OUT.texcoord = IN.texcoord;             return OUT;         }           sampler2D _MainTex;         float _SwitchColor;         float _Alpha;         float4 _ChooseColor;         float4 _HighlightColor;         int _ChooseR;         int _ChooseG;         int _ChooseB;         int _ThresholdValue;         float4 frag(v2f IN) : SV_Target         {         if (_SwitchColor == 0)         {             return 0;         }         // sample the texture         float4 col = tex2D(_MainTex, IN.texcoord);               return  step(         3         , step(abs(_ChooseR - col.r * 255), _ThresholdValue)         + step(abs(_ChooseG - col.g * 255), _ThresholdValue)         + step(abs(_ChooseB - col.b * 255), _ThresholdValue)         )*_HighlightColor;           }             ENDCG         }         } }