[net11.0] Make iOS image scaling deadlock-safe

src/Graphics/src/Graphics/Platforms/iOS/UIImageExtensions.cs

@@ -56,12 +56,40 @@ internal static UIImage ResizeImageSource(this UIImage sourceImage, nfloat maxWi
 
 		public static UIImage ScaleImage(this UIImage target, CGSize size, bool disposeOriginal = false)
 		{
-#pragma warning disable CA1416 // Preserve the existing rendering behavior while these unsupported APIs are replaced.
-			UIGraphics.BeginImageContext(size);
-			target.Draw(new CGRect(CGPoint.Empty, size));
-			var image = UIGraphics.GetImageFromCurrentImageContext();
-			UIGraphics.EndImageContext();
-#pragma warning restore CA1416
+			if (!(size.Width > 0) || !(size.Height > 0) ||
+				double.IsInfinity(size.Width) || double.IsInfinity(size.Height))
+			{
+				return target;
+			}
+
+			var width = checked((int)Math.Ceiling(size.Width));
+			var height = checked((int)Math.Ceiling(size.Height));
+
+			using var colorSpace = CGColorSpace.CreateDeviceRGB();
+			using var context = new CGBitmapContext(
+				IntPtr.Zero,
+				width,
+				height,
+				8,
+				checked(4 * width),
+				colorSpace,
+				CGBitmapFlags.ByteOrder32Little | CGBitmapFlags.PremultipliedFirst);
+
+			context.TranslateCTM(0, height);
+			context.ScaleCTM(1, -1);
+
+			UIGraphics.PushContext(context);
+			try
+			{
+				target.Draw(new CGRect(CGPoint.Empty, size));
+			}
+			finally
+			{
+				UIGraphics.PopContext();
+			}
+
+			using var cgImage = context.ToImage();
+			var image = UIImage.FromImage(cgImage, 1, UIImageOrientation.Up);
 
 			if (disposeOriginal)
 			{

src/Graphics/tests/DeviceTests/Tests/ImageTests.cs

@@ -84,6 +84,25 @@ public void ScaleImageUsesOneXBackingScale(float sourceScale)
 		Assert.Equal(5, (int)scaled.CGImage.Height);
 	}
 
+	[Theory]
+	[InlineData(0, 10)]
+	[InlineData(10, 0)]
+	[InlineData(-1, 10)]
+	[InlineData(10, -1)]
+	[InlineData(double.NaN, 10)]
+	[InlineData(10, double.NaN)]
+	[InlineData(double.PositiveInfinity, 10)]
+	[InlineData(10, double.PositiveInfinity)]
+	public void ScaleImageReturnsOriginalForNonPositiveSize(double width, double height)
+	{
+		using var source = CreatePatternImage(UIImageOrientation.Up);
+
+		var scaled = source.ScaleImage(new CGSize(width, height), disposeOriginal: true);
+
+		Assert.Same(source, scaled);
+		Assert.NotNull(scaled.CGImage);
+	}
+
 	[Fact]
 	public async Task ScaleImageCanRunOnBackgroundThread()
 	{
@@ -162,6 +181,10 @@ public void ScaleImageMatchesUIKitRendering(UIImageOrientation orientation)
 
 		Assert.Equal(UIImageOrientation.Up, actual.Orientation);
 		Assert.Equal(GetPixelData(expected), GetPixelData(actual));
+		Assert.Equal(expected.CGImage.Width, actual.CGImage.Width);
+		Assert.Equal(expected.CGImage.Height, actual.CGImage.Height);
+		Assert.Equal(13, (double)actual.Size.Width);
+		Assert.Equal(9, (double)actual.Size.Height);
 	}
 
 	private static UIImage CreatePatternImage(UIImageOrientation orientation)