- GIF animation custom control for WPF: When BitmapImage load from Uri, this UI control can animate, however, when from Stream, this UI control "cannot" animate (BitmapImage load only 1 frame). - WPF のための GIF アニメーションカスタムコントロール: BitmapImage で、Uri から読み込んだとき、UI コントロールはアニメーションできます。しかし、Stream から読み込んだとき、アニメーションできません (何故ならば、BitmapImage は 1 フレームしか読み込まない…

AnimatedImage.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;

namespace Mntone.CustomControls
{
	public class AnimatedImage: Image
	{
		public bool IsAnimationWorking { get; private set; }
		private Int32Animation _animation = null;
		private BitmapDecoder _decoder = null;
		private BitmapMetadata _metadata = null;

		private ushort _delay = 0;

		private void ClearAnimation()
		{
			if( _animation != null )
				BeginAnimation( FrameIndexProperty, null );

			IsAnimationWorking = false;
			_animation = null;
			_decoder = null;
			_metadata = null;
			_delay = 0;
		}

		private void PrepareAnimation( BitmapImage bi )
		{
			if( _decoder.Frames.Count == 1)
			{
				base.Source = _decoder.Frames[0];
				return;
			}

			_metadata = ( BitmapMetadata )_decoder.Frames[0].Metadata;
			var od = _metadata.GetQuery( "/grctlext/Delay" );
			_delay = ( ushort )od;

			var ts = TimeSpan.FromMilliseconds( _decoder.Frames.Count * 10 * ( double )_delay );
			_animation = new Int32Animation( 0, _decoder.Frames.Count - 1, new Duration( ts ), FillBehavior.Stop ) { RepeatBehavior = RepeatBehavior.Forever };

			base.Source = _decoder.Frames[0];
			BeginAnimation( FrameIndexProperty, _animation );
			IsAnimationWorking = true;
		}


		private bool IsAnimatedGifImage( BitmapImage bi )
		{
			var flag = false;
			if( bi.UriSource != null )
			{
				_decoder = BitmapDecoder.Create( bi.UriSource, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad );
				flag = _decoder.GetType() == typeof( GifBitmapDecoder ) && _decoder.Frames.Count > 1;
			}
			else if( bi.StreamSource != null )
			{
				try
				{
					//bi.StreamSource.Position = 0;
					_decoder = BitmapDecoder.Create( bi.StreamSource, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad );
					flag = _decoder.GetType() == typeof( GifBitmapDecoder ) && _decoder.Frames.Count > 1;
				}
				catch
				{
					flag = false;
				}
			}

			if( !flag && _decoder != null )
				_decoder = null;

			return flag;
		}

		protected virtual void OnChangingFrameIndex( DependencyPropertyChangedEventArgs args )
		{
			var idx = ( int )args.NewValue;
			base.Source = _decoder.Frames[idx];
			InvalidateVisual();
		}

		protected virtual void OnSourceChanged( DependencyPropertyChangedEventArgs args )
		{
			ClearAnimation();

			var bi = args.NewValue as BitmapImage;
			if( bi == null )
			{
				var source = args.NewValue as ImageSource;
				base.Source = source;
				return;
			}

			if( !IsAnimatedGifImage( bi ) )
			{
				base.Source = bi;
				return;
			}

			PrepareAnimation( bi );
		}

		private static void ChangingFrameIndex( DependencyObject obj, DependencyPropertyChangedEventArgs args )
		{
			var ai = obj as AnimatedImage;
			if( ai == null || !ai.IsAnimationWorking )
				return;

			ai.OnChangingFrameIndex( args );
		}

		private static void OnSourceChanged( DependencyObject obj, DependencyPropertyChangedEventArgs args )
		{
			var ai = obj as AnimatedImage;
			if( ai == null )
				return;

			ai.OnSourceChanged( args );
		}

		#region 依存プロパティー

		public uint FrameIndex
		{
			get { return ( uint )GetValue( FrameIndexProperty ); }
			set { SetValue( FrameIndexProperty, value ); }
		}
		public static readonly DependencyProperty FrameIndexProperty
			= DependencyProperty.Register( "FrameIndex", typeof( int ), typeof( AnimatedImage ), new UIPropertyMetadata( 0, ChangingFrameIndex ) );

		public new ImageSource Source
		{
			get { return ( ImageSource )GetValue( SourceProperty ); }
			set { SetValue( SourceProperty, value ); }
		}
		public static readonly new DependencyProperty SourceProperty
			= DependencyProperty.Register(
				"Source",
				typeof( ImageSource ),
				typeof( AnimatedImage ),
				new FrameworkPropertyMetadata( null, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.AffectsMeasure, OnSourceChanged ) );

		#endregion
	}
}