public class Particle
 {
    /// <summary>
    /// 形狀
    /// </summary>
    public Ellipse Shape;
    /// <summary>
    /// 坐標
    /// </summary>
    public Point Position;
}

/// <summary>
/// 粒子路徑
/// </summary>
private Geometry particleGeometry;
 
/// <summary>
/// 粒子個數
/// </summary>
private int particleCount = 100;
 
/// <summary>
/// 粒子最小尺寸
/// </summary>
private static int sizeMin = 10;
 
/// <summary>
/// 粒子最大尺寸
/// </summary>
private int sizeMax = 20;
 
/// <summary>
/// 隨機數
/// </summary>
private Random random;
 
/// <summary>
/// 粒子列表
/// </summary>
private List<Particle> particles;
 
/// <summary>
/// 粒子容器
/// </summary>
private Canvas containerParticles;
 
 
    public ParticleSystem(Geometry _path, int _maxRadius, int _particleCount, Canvas _containerParticles)
    {
      particleGeometry = _path;
      particleCount = _particleCount;
      sizeMax = _maxRadius;
      containerParticles = _containerParticles;
      random = new Random();
      particles = new List<Particle>();
      SpawnParticle();
    }
 
    /// <summary>
    /// 初始化粒子
    /// </summary>
    private void SpawnParticle()
    {
      //清空粒子隊列
      particles.Clear();
      containerParticles.Children.Clear();
 
      //生成粒子
      for (int i = 0; i < particleCount; i++)
      {
        double size = random.Next(sizeMin, sizeMax + 1);
        while(true)
        {
          Point po = new Point(random.Next((int)particleGeometry.Bounds.Left, (int)particleGeometry.Bounds.Right), random.Next((int)particleGeometry.Bounds.Top, (int)particleGeometry.Bounds.Bottom));
          if (particleGeometry.FillContains(po, 2, ToleranceType.Absolute))
          {
            Particle p = new Particle
            {
              Shape = new Ellipse
              {
                Width = size,
                Height = size,
                Stretch = System.Windows.Media.Stretch.Fill,
                Fill = GetRandomColorBursh(),
              },
              Position = po,
            };
            SetParticleSizeAnimation(p.Shape);
            particles.Add(p);
            Canvas.SetLeft(p.Shape, p.Position.X);
            Canvas.SetTop(p.Shape, p.Position.Y);
            containerParticles.Children.Add(p.Shape);
            break;
          }
        }
      }
    }
 
    /// <summary>
    /// 設置粒子大小動畫
    /// </summary>
    private void SetParticleSizeAnimation(Ellipse p)
    {
      Storyboard sb = new Storyboard();
      //動畫完成事件 再次設置此動畫
      sb.Completed += (S, E) =>
      {
        SetParticleSizeAnimation(p);
      };
      int size = random.Next(sizeMin, sizeMax + 1);
      int time = random.Next(100, 1000);
      DoubleAnimation daX = new DoubleAnimation(size, new Duration(TimeSpan.FromMilliseconds(time)));
      DoubleAnimation daY = new DoubleAnimation(size, new Duration(TimeSpan.FromMilliseconds(time)));
      Storyboard.SetTarget(daX, p);
      Storyboard.SetTarget(daY, p);
      Storyboard.SetTargetProperty(daX, new PropertyPath("Width"));
      Storyboard.SetTargetProperty(daY, new PropertyPath("Height"));
      sb.Children.Add(daX);
      sb.Children.Add(daY);
      sb.Begin();
    }
 
    /// <summary>
    /// 獲取隨機顏色畫刷
    /// </summary>
    private SolidColorBrush GetRandomColorBursh()
    {
      byte r = (byte)random.Next(128, 256);
      byte g = (byte)random.Next(128, 256);
      byte b = (byte)random.Next(128, 256);
      return new SolidColorBrush(Color.FromArgb(125, r, g, b));
}

private ParticleSystem ps;
 
public MainWindow()
    {
      InitializeComponent();
      this.Loaded += MainWindow_Loaded;
    }
 
    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
      Geometry g = CreateTextPath("H E L L O", new Point(this.cvs_particleContainer.Margin.Left, this.cvs_particleContainer.Margin.Top), new Typeface(new FontFamily("Arial"), FontStyles.Normal, FontWeights.Bold, FontStretches.Normal), 200);
      ps = new ParticleSystem(g, 25, 350, this.cvs_particleContainer);
    }
 
    /// <summary>
    /// 創建文本路徑
    /// </summary>
    /// <param name="word">文本字符串</param>
    /// <param name="point">顯示位置</param>
    /// <param name="typeface">字體信息</param>
    /// <param name="fontSize">字體大小</param>
    /// <returns></returns>
    private Geometry CreateTextPath(string word, Point point, Typeface typeface, int fontSize)
    {
      FormattedText text = new FormattedText(word, new System.Globalization.CultureInfo("en-US"), FlowDirection.LeftToRight, typeface, fontSize, Brushes.Black);
      Geometry g = text.BuildGeometry(point);
      PathGeometry path = g.GetFlattenedPathGeometry();
      return path;
}