[Windows] Fix image button scaling

src/Controls/samples/Controls.Sample.UITests/Issues/Issue18242.xaml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+			 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+			 x:Class="Maui.Controls.Sample.Issues.Issue18242"
+			 Title="Issue 18242">
+	<VerticalStackLayout
+		Padding="12">
+		<Label
+			AutomationId="WaitForStubControl"
+			Text="1. The image must adapt to the size of the Button and be in the position determined by the ContentLayout property."/>
+		<Label 
+			Text="Button with Height"/>
+		<Button
+			HeightRequest="50"
+			ImageSource="dotnet_bot.png"
+			ContentLayout="Left,10"
+			Text="Button"/>
+		<Label 
+			Text="Button without Height"/>
+		<Button
+			ImageSource="dotnet_bot.png"
+			ContentLayout="Left,10"
+			Text="Button"/>
+		<Label 
+			Text="2. The image must adapt to the size of the ImageButton."/>
+		<Label 
+			Text="ImageButton with Height"/>
+		<ImageButton 
+			HeightRequest="30" 
+			WidthRequest="50" 
+			Source="dotnet_bot.png"/>
+		<Label 
+		   Text="ImageButton without Height"/>
+		<ImageButton 
+		   WidthRequest="50" 
+		   Source="dotnet_bot.png"/>
+	</VerticalStackLayout>
+</ContentPage>

src/Controls/samples/Controls.Sample.UITests/Issues/Issue18242.xaml.cs

@@ -0,0 +1,15 @@
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 18242, "Button ImageSource not Scaling as expected", PlatformAffected.UWP)]
+	public partial class Issue18242 : ContentPage
+	{
+		public Issue18242()
+		{
+			InitializeComponent();
+		}
+	}
+}

src/Controls/tests/UITests/Tests/Issues/Issue18242.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.AppiumTests.Issues
+{
+	public class Issue18242 : _IssuesUITest
+	{
+		public Issue18242(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "Button ImageSource not Scaling as expected";
+
+		[Test]
+		public void Issue18242Test()
+		{
+			this.IgnoreIfPlatforms(new TestDevice[] { TestDevice.Android, TestDevice.Mac, TestDevice.iOS }, "Only Windows for now");
+
+			App.WaitForElement("WaitForStubControl");
+
+			VerifyScreenshot();
+		}
+	}
+}

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

@@ -159,11 +159,9 @@ public static void UpdateImageSource(this Button platformButton, WImageSource? n
 		{
 			if (platformButton.GetContent<WImage>() is WImage nativeImage)
 			{
-				nativeImage.Source = nativeImageSource;
-
 				// Stretch to the size of the button
-				nativeImage.HorizontalAlignment = UI.Xaml.HorizontalAlignment.Stretch;
-				nativeImage.VerticalAlignment = UI.Xaml.VerticalAlignment.Stretch;
+				nativeImage.Stretch = UI.Xaml.Media.Stretch.Uniform;
+				nativeImage.Source = nativeImageSource;
 
 				nativeImage.Visibility = nativeImageSource == null
 					? UI.Xaml.Visibility.Collapsed