tweaks and fixes to acrylic.

samples/ControlCatalog/Pages/AcrylicPage.xaml

@@ -71,7 +71,7 @@
         <Border Height="200" Width="200" CornerRadius="5" BoxShadow="2 2 16 0 Black">
           <Border.Background>
             <ExperimentalAcrylicBrush
-              TintColor="Black"
+              TintColor="White"
               TintOpacity="{Binding #TintOpacitySlider.Value}"
               BackgroundSource="Digger" />
           </Border.Background>
@@ -89,8 +89,8 @@
         <Border Height="200" Width="200" CornerRadius="5" BoxShadow="2 2 16 0 Black">
           <Border.Background>
             <ExperimentalAcrylicBrush
-              TintColor="White"
-              TintOpacity="{Binding #TintOpacitySlider.Value}"
+              TintColor="{StaticResource SystemChromeAltHighColor}"
+              TintOpacity="0.8"              
               BackgroundSource="Digger" />
           </Border.Background>
         </Border>

src/Avalonia.Visuals/Media/ExperimentalAcrylicBrush.cs

@@ -135,7 +135,7 @@ namespace Avalonia.Media
 
             if (false) // non-acrylic blue // TODO detect blur level.
             {
-                tintColor = new Color((byte)(Math.Round(tintColor.A * (((tintOpacity * tintOpacityModifier) * 0.25) + 0.75))), tintColor.R, tintColor.G, tintColor.B);
+                tintColor = new Color((byte)(Math.Round(tintColor.A * (((tintOpacity * tintOpacityModifier) * 0.15) + 0.85))), tintColor.R, tintColor.G, tintColor.B);
             }
             else
             {
@@ -157,7 +157,7 @@ namespace Avalonia.Media
 
             const double whiteMaxOpacity = 0.40; // 100% luminosity
             const double midPointMaxOpacity = 0.50; // 50% luminosity
-            const double blackMaxOpacity = 0.60; // 0% luminosity
+            const double blackMaxOpacity = 0.80; // 0% luminosity
             
             var hsv = RgbToHsv(tintColor);
 

src/Skia/Avalonia.Skia/DrawingContextImpl.cs

@@ -697,10 +697,10 @@ namespace Avalonia.Skia
                     acrylicBrush.BackgroundSource == AcrylicBackgroundSource.Digger ?
                     acrylicBrush.TintOpacity : 1;
 
-                const double noiseOpcity = 0.02;
+                const double noiseOpcity = 0.0225;
 
                 var tintColor = acrylicBrush.TintColor;                
-                var tint = new SKColor(tintColor.R, tintColor.G, tintColor.B, (byte)(255 * ((tintColor.A / 255.0) * acrylicBrush.Opacity)));                
+                var tint = new SKColor(tintColor.R, tintColor.G, tintColor.B, (byte)(255 * ((tintColor.A / 255.0) * acrylicBrush.Opacity * tintOpacity)));                
                 
                 if(s_acrylicNoiseShader == null)
                 {