Fix CanvasImageSource scaling behavior (#21239)

Co-authored-by: Mike Corsaro <mikecorsaro@microsoft.com>

src/Core/src/Platform/Windows/ButtonExtensions.cs

@@ -1,4 +1,5 @@
 #nullable enable
+using Microsoft.Graphics.Canvas.UI.Xaml;
 using Microsoft.Maui.Graphics;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
@@ -159,10 +160,18 @@ public static void UpdateImageSource(this Button platformButton, WImageSource? n
 		{
 			if (platformButton.GetContent<WImage>() is WImage nativeImage)
 			{
-				// Stretch to the size of the button
+				// Stretch to fill
 				nativeImage.Stretch = UI.Xaml.Media.Stretch.Uniform;
 				nativeImage.Source = nativeImageSource;
 
+				// If we're a CanvasImageSource (font image source), we need to explicitly set the image height
+				// to the desired size of the font, otherwise it will be stretched to the available space
+				if (nativeImage.Source is CanvasImageSource canvas)
+				{
+					nativeImage.Width = canvas.Size.Width;
+					nativeImage.Height = canvas.Size.Height;
+				}
+
 				nativeImage.Visibility = nativeImageSource == null
 					? UI.Xaml.Visibility.Collapsed
 					: UI.Xaml.Visibility.Visible;