Animated WPF Panels

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media.Imaging;
using Bornander.UI.Animations;
using Bornander.UI.Animations.Animators;

namespace Bornander.UI.Test
{
    public partial class GridBackground : Window
    {
        private const int NumberOfRows = 4;
        private const int NumberOfColumns = 4;
        private const double DesiredAspectRatio = 1024.0 / 768.0;

        private readonly Random random = new Random();

        private IDictionary<string, IList<UIElement>> backgrounds = new Dictionary<string, IList<UIElement>>(); 

        public GridBackground()
        {
            InitializeComponent();

            backgroundGrid.SizeChanged += GridBackground_SizeChanged;
            backgroundGrid.Animator = new FractionDistanceAnimator(0.1);

            foreach (string name in new[] { "Jellyfish", "Koala", "Penguins" })
            {
                backgrounds[name] = new List<UIElement>();
                BitmapSource[,] tiles = SplitImage(LoadImage(String.Format(@"Images\{0}.jpg", name)), NumberOfRows, NumberOfColumns);
                for (int row = 0; row < NumberOfRows; ++row)
                {
                    for (int column = 0; column < NumberOfColumns; ++column)
                    {
                        Image image = new Image();
                        image.Source = tiles[row, column];
                        image.SetValue(Grid.RowProperty, row);
                        image.SetValue(Grid.ColumnProperty, column);
                        backgroundGrid.Children.Add(image);
                        backgrounds[name].Add(image);
                    }
                }
            }

            RecalculateOffscreenPoints();

            SizeChanged += (s, e) => RecalculateOffscreenPoints();
        }

        private void RecalculateOffscreenPoints()
        {
            foreach (UIElement element in backgroundGrid.Children)
            {
                element.SetValue(AnimationBase.OverridePositionProperty, GenerateOffscreenPoint());
            }
        }

        private Point GenerateOffscreenPoint()
        {
            double radius = Math.Max(backgroundGrid.ActualWidth, backgroundGrid.ActualHeight) + Math.Max(backgroundGrid.ActualWidth / (double)NumberOfColumns, backgroundGrid.ActualHeight / (double)NumberOfRows);
            return new Point
                (
                (backgroundGrid.ActualWidth / 2.0) + Math.Cos(random.NextDouble() * 2.0 * Math.PI) * radius,
                (backgroundGrid.ActualHeight / 2.0) + Math.Sin(random.NextDouble() * 2.0 * Math.PI) * radius
                );

        }

        void GridBackground_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            double ratio = e.NewSize.Width / e.NewSize.Height;
            if (ratio != DesiredAspectRatio)
            {
                backgroundGrid.Height = e.NewSize.Width / DesiredAspectRatio;
            }

        }

        private static BitmapSource LoadImage(string filename)
        {
            BitmapImage image = new BitmapImage();
            image.BeginInit();
            image.UriSource = new Uri(filename, UriKind.RelativeOrAbsolute);
            image.EndInit();

            return image;
        }

        private static BitmapSource[,] SplitImage(BitmapSource source, int rows, int columns)
        {
            BitmapSource[,] result = new BitmapSource[rows, columns];

            int width = (int)(source.Width / columns);
            int height = (int)(source.Height / rows);

            for (int row = 0; row < rows; ++row)
            {
                for(int column = 0; column < columns; ++column)
                {
                    result[row, column] = new CroppedBitmap(source, new Int32Rect(column * width, row * height, width, height));  
                }
            }

            return result;
        }

        private void ToggleBackground(string name)
        {
            foreach (UIElement element in backgroundGrid.Children)
            {
                element.SetValue(AnimationBase.OverrideArrangeProperty, true);
            }

            foreach (UIElement element in backgrounds[name])
            {
                element.SetValue(AnimationBase.OverrideArrangeProperty, false);
            }
        }

        private void Jellyfish_Click(object sender, RoutedEventArgs e)
        {

            ToggleBackground("Jellyfish");
        }

        private void Koala_Click(object sender, RoutedEventArgs e)
        {
            ToggleBackground("Koala");
        }
        
        private void Penguins_Click(object sender, RoutedEventArgs e)
        {
            ToggleBackground("Penguins");
        }
    }
}