Update dispersion shader

backdrop/src/main/java/com/kyant/backdrop/Shaders.kt

@@ -87,10 +87,6 @@ float circleMap(float x) {
     return 1.0 - sqrt(1.0 - x * x);
 }
 
-float2 normalToTangent(float2 normal) {
-    return float2(normal.y, -normal.x);
-}
-
 half4 main(float2 coord) {
     float2 halfSize = size * 0.5;
     float2 centeredCoord = coord - halfSize;
@@ -109,7 +105,7 @@ half4 main(float2 coord) {
     float4 maxGradRadius = float4(min(halfSize.x, halfSize.y));
     float4 gradRadius = min(cornerRadius * 1.5, maxGradRadius);
     float2 normal = gradSdRoundedRectangle(centeredCoord, halfSize, gradRadius);
-    float2 tangent = normalToTangent(normal);
+    float2 tangent = float2(normal.y, -normal.x);
     
     half4 dispersedColor = half4(0.0);
     half4 weight = half4(0.0);
@@ -121,14 +117,12 @@ half4 main(float2 coord) {
         half rMask = step(0.5, t);
         half gMask = step(0.25, t) * step(t, 0.75);
         half bMask = step(t, 0.5);
-        half4 mask = half4(rMask, gMask, bMask, 0.0);
+        half4 mask = half4(rMask, gMask, bMask, 1.0);
         dispersedColor += color * mask;
         weight += mask;
     }
-    dispersedColor /= weight;
     
-    dispersedColor.a = image.eval(coord).a;
-    return dispersedColor;
+    return dispersedColor / weight;
 }"""
 
 @Language("AGSL")