Use my home-made GIF and APNG animator. It's really save CPU compared to previous one!

QuickLook.Plugin/QuickLook.Plugin.ImageViewer/AnimatedImage/AnimatedImage.cs

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+// Copyright © 2017 Paddy Xu
+// 
+// This file is part of QuickLook program.
+// 
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+using System;
+using System.IO;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media.Animation;
+
+namespace QuickLook.Plugin.ImageViewer.AnimatedImage
+{
+    public class AnimatedImage : Image, IDisposable
+    {
+        public static readonly DependencyProperty AnimationUriProperty =
+            DependencyProperty.Register("AnimationUri", typeof(Uri), typeof(AnimatedImage),
+                new UIPropertyMetadata(null, LoadImage));
+
+        private readonly ObjectAnimationUsingKeyFrames _animator = new ObjectAnimationUsingKeyFrames();
+
+        public Uri AnimationUri
+        {
+            get => (Uri) GetValue(AnimationUriProperty);
+            set => SetValue(AnimationUriProperty, value);
+        }
+
+        public void Dispose()
+        {
+            BeginAnimation(SourceProperty, null);
+            Source = null;
+            _animator.KeyFrames.Clear();
+        }
+
+        private static void LoadImage(DependencyObject obj, DependencyPropertyChangedEventArgs ev)
+        {
+            var instance = obj as AnimatedImage;
+            if (instance == null)
+                return;
+
+            var path = ((Uri) ev.NewValue).LocalPath;
+            var ext = Path.GetExtension(path).ToLower();
+
+            IAnimationProvider provider;
+
+            switch (ext)
+            {
+                case ".gif":
+                    provider = new GIFAnimationProvider();
+                    break;
+                case ".png":
+                    provider = new APNGAnimationProvider();
+                    break;
+                default:
+                    provider = new ImageMagickProvider();
+                    break;
+            }
+
+            provider.GetAnimator(instance._animator, path);
+
+            instance.BeginAnimation(SourceProperty, instance._animator);
+        }
+    }
+}