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65 行
1.3 KiB
65 行
1.3 KiB
// Reduces input image (_MainTex) by 2x2.
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// Outputs maximum value in R, minimum in G.
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Shader "Hidden/Contrast Stretch Reduction" {
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Properties {
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_MainTex ("Base (RGB)", 2D) = "white" {}
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}
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Category {
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SubShader {
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Pass {
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ZTest Always Cull Off ZWrite Off
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CGPROGRAM
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#pragma vertex vert
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#pragma fragment frag
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#include "UnityCG.cginc"
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struct v2f {
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float4 position : SV_POSITION;
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float2 uv[4] : TEXCOORD0;
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};
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uniform sampler2D _MainTex;
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v2f vert (appdata_img v) {
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v2f o;
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o.position = mul (UNITY_MATRIX_MVP, v.vertex);
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float2 uv = MultiplyUV (UNITY_MATRIX_TEXTURE0, v.texcoord);
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// Compute UVs to sample 2x2 pixel block.
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o.uv[0] = uv + float2(0,0);
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o.uv[1] = uv + float2(0,1);
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o.uv[2] = uv + float2(1,0);
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o.uv[3] = uv + float2(1,1);
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return o;
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}
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float4 frag (v2f i) : SV_Target
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{
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// Sample pixel block
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float4 v00 = tex2D(_MainTex, i.uv[0]);
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float2 v01 = tex2D(_MainTex, i.uv[1]).xy;
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float2 v10 = tex2D(_MainTex, i.uv[2]).xy;
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float2 v11 = tex2D(_MainTex, i.uv[3]).xy;
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float4 res;
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// output x: maximum of the four values
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res.x = max( max(v00.x,v01.x), max(v10.x,v11.x) );
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// output y: minimum of the four values
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res.y = min( min(v00.y,v01.y), min(v10.y,v11.y) );
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// output zw unchanged from the first pixel
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res.zw = v00.zw;
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return res;
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}
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ENDCG
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}
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}
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}
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Fallback off
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}
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