[Avalonia] Animated Gifs and Webp #150

src/PicView.Avalonia/AnimatedImage/CustomVisualHandler.cs

@@ -0,0 +1,74 @@
+using Avalonia;
+using Avalonia.Logging;
+using Avalonia.Media;
+using Avalonia.Rendering.Composition;
+
+namespace PicView.Avalonia.AnimatedImage;
+
+public class CustomVisualHandler : CompositionCustomVisualHandler
+{
+    private TimeSpan _animationElapsed;
+    private TimeSpan? _lastServerTime;
+    private IGifInstance? _currentInstance;
+    private bool _running;
+
+    public static readonly object StopMessage = new(),
+        StartMessage = new();
+
+    public override void OnMessage(object message)
+    {
+        if (message == StartMessage)
+        {
+            _running = true;
+            _lastServerTime = null;
+            RegisterForNextAnimationFrameUpdate();
+        }
+        else if (message == StopMessage)
+        {
+            _running = false;
+        }
+        else if (message is IGifInstance instance)
+        {
+            _currentInstance?.Dispose();
+            _currentInstance = instance;
+        }
+    }
+
+    public override void OnAnimationFrameUpdate()
+    {
+        if (!_running)
+            return;
+        Invalidate();
+        RegisterForNextAnimationFrameUpdate();
+    }
+
+    public override void OnRender(ImmediateDrawingContext drawingContext)
+    {
+        if (_running)
+        {
+            if (_lastServerTime.HasValue)
+                _animationElapsed += (CompositionNow - _lastServerTime.Value);
+            _lastServerTime = CompositionNow;
+        }
+
+        try
+        {
+            if (_currentInstance is null || _currentInstance.IsDisposed)
+                return;
+
+            var bitmap = _currentInstance.ProcessFrameTime(_animationElapsed);
+            if (bitmap is not null)
+            {
+                drawingContext.DrawBitmap(
+                    bitmap,
+                    new Rect(_currentInstance.GifPixelSize.ToSize(1)),
+                    GetRenderBounds()
+                );
+            }
+        }
+        catch (Exception e)
+        {
+            Logger.Sink?.Log(LogEventLevel.Error, "GifImage Renderer ", this, e.ToString());
+        }
+    }
+}

src/PicView.Avalonia/AnimatedImage/Decoding/BlockTypes.cs

@@ -0,0 +1,9 @@
+namespace PicView.Avalonia.AnimatedImage.Decoding;
+internal enum BlockTypes
+{
+    Empty = 0,
+    Extension = 0x21,
+    ImageDescriptor = 0x2C,
+    Trailer = 0x3B,
+}
+

src/PicView.Avalonia/AnimatedImage/Decoding/ExtensionType.cs

@@ -0,0 +1,7 @@
+namespace PicView.Avalonia.AnimatedImage.Decoding;
+internal enum ExtensionType
+{
+    GraphicsControl = 0xF9,
+    Application = 0xFF
+}
+

src/PicView.Avalonia/AnimatedImage/Decoding/FrameDisposal.cs

@@ -0,0 +1,9 @@
+namespace PicView.Avalonia.AnimatedImage.Decoding;
+public enum FrameDisposal
+{
+    Unknown = 0,
+    Leave = 1,
+    Background = 2,
+    Restore = 3
+}
+

src/PicView.Avalonia/AnimatedImage/Decoding/GifColor.cs

@@ -0,0 +1,36 @@
+using System.Runtime.InteropServices;
+
+namespace PicView.Avalonia.AnimatedImage.Decoding;
+
+[StructLayout(LayoutKind.Explicit)]
+public readonly struct GifColor
+{
+    [FieldOffset(3)]
+    public readonly byte A;
+
+    [FieldOffset(2)]
+    public readonly byte R;
+
+    [FieldOffset(1)]
+    public readonly byte G;
+
+    [FieldOffset(0)]
+    public readonly byte B;
+
+    /// <summary>
+    /// A struct that represents a ARGB color and is aligned as
+    /// a BGRA bytefield in memory.
+    /// </summary>
+    /// <param name="r">Red</param>
+    /// <param name="g">Green</param>
+    /// <param name="b">Blue</param>
+    /// <param name="a">Alpha</param>
+    public GifColor(byte r, byte g, byte b, byte a = byte.MaxValue)
+    {
+        A = a;
+        R = r;
+        G = g;
+        B = b;
+    }
+}
+