Add transparent bitmap support for credential tiles

src/Lithnet.CredentialProvider.UnitTests.x64/BitmapControlTests.cs

@@ -0,0 +1,97 @@
+using System;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.IO;
+using System.Runtime.InteropServices;
+using NUnit.Framework;
+
+namespace Lithnet.CredentialProvider.UnitTests
+{
+    public class BitmapControlTests
+    {
+        [Test]
+        public void TransparentBufferPreservesAlphaChannel()
+        {
+            using (Bitmap source = new Bitmap(2, 1, PixelFormat.Format32bppArgb))
+            {
+                source.SetPixel(0, 0, Color.FromArgb(0, 10, 20, 30));
+                source.SetPixel(1, 0, Color.FromArgb(128, 40, 50, 60));
+
+                var control = new UserTileControl("image", "Image", source);
+
+                byte[] bytes = GetBitmapBuffer(control);
+
+                Assert.That(bytes, Has.Length.GreaterThan(8));
+                Assert.That(bytes[0], Is.EqualTo(0x89));
+                Assert.That(bytes[1], Is.EqualTo(0x50));
+                Assert.That(bytes[2], Is.EqualTo(0x4e));
+                Assert.That(bytes[3], Is.EqualTo(0x47));
+
+                using (MemoryStream stream = new MemoryStream(bytes))
+                using (Bitmap decoded = new Bitmap(stream))
+                {
+                    Assert.That(decoded.GetPixel(0, 0).A, Is.EqualTo(0));
+                    Assert.That(decoded.GetPixel(1, 0).A, Is.EqualTo(128));
+                    Assert.That(decoded.GetPixel(1, 0).R, Is.EqualTo(40));
+                    Assert.That(decoded.GetPixel(1, 0).G, Is.EqualTo(50));
+                    Assert.That(decoded.GetPixel(1, 0).B, Is.EqualTo(60));
+                }
+            }
+        }
+
+        [Test]
+        public void BitmapBufferDoesNotApplyConfiguredBackgroundColor()
+        {
+            using (Bitmap source = new Bitmap(1, 1, PixelFormat.Format32bppArgb))
+            {
+                source.SetPixel(0, 0, Color.Transparent);
+
+                var control = new UserTileControl("image", "Image", source)
+                {
+                    BackgroundColor = Color.FromArgb(12, 34, 56)
+                };
+
+                byte[] bytes = GetBitmapBuffer(control);
+
+                using (MemoryStream stream = new MemoryStream(bytes))
+                using (Bitmap decoded = new Bitmap(stream))
+                {
+                    Assert.That(decoded.GetPixel(0, 0).A, Is.EqualTo(0));
+                }
+            }
+        }
+
+        [Test]
+        public void CloneCopiesBitmapAndBackgroundColor()
+        {
+            using (Bitmap source = new Bitmap(1, 1))
+            {
+                var control = new UserTileControl("image", "Image", source)
+                {
+                    BackgroundColor = Color.CornflowerBlue
+                };
+
+                var clone = (UserTileControl)control.Clone();
+
+                Assert.That(clone.Bitmap, Is.SameAs(source));
+                Assert.That(clone.BackgroundColor, Is.EqualTo(Color.CornflowerBlue));
+            }
+        }
+
+        private static byte[] GetBitmapBuffer(BitmapControl control)
+        {
+            IntPtr buffer = control.GetBitmapBuffer(out uint size);
+
+            try
+            {
+                byte[] bytes = new byte[size];
+                Marshal.Copy(buffer, bytes, 0, checked((int)size));
+                return bytes;
+            }
+            finally
+            {
+                Marshal.FreeCoTaskMem(buffer);
+            }
+        }
+    }
+}