Silverlight 引路蜂二维图形库示例:动画Beziers曲线

类Path为一条几何路径，可以通过直线，二次曲线，三次曲线来构成任意路径。Path提供了moveTo, lineTo, curveTo, curveToCubic, closePath方法来构成路径。

下面的例子动态显示一条Bezier曲线。

/**
* The animation thread.
*/
Thread _thread;
bool _drawn;
/**
 * The random number generator.
 */
readonly Random _random = new Random();
/**
 * The animated path
 */
readonly Path _path = new Path();
/**
 * Red brush used to fill the path.
 */
readonly SolidBrush _brush = new SolidBrush(Color.Red);
const int Numpts = 6;
readonly int[] _animpts = new int[Numpts * 2];
readonly int[] _deltas = new int[Numpts * 2];

private void Beziers()
{
 Reset(screenWidth, screenHeight);
 _thread = new Thread(RunBeziers);
 _thread.Start();
}

private void RunBeziers()
{

 Thread me = Thread.CurrentThread;

 if (!_drawn)
 {
  lock (this)
  {
   graphics2D.Clear(Color.White);
   graphics2D.Fill(_brush, _path);
   _drawn = true;
  }
 }
 while (_thread == me)
 {
  DrawDemo(screenWidth, screenHeight);
 }
}

/**
* Generates new points for the path.
*/
private void Animate(int[] pts, int[] deltas, int i, int limit)
{
 int newpt = pts[i] + deltas[i];
 if (newpt <= 0)
 {
  newpt = -newpt;
  deltas[i] = (_random.Next() & 0x00000003) + 2;
 }
 else if (newpt >= limit)
 {
  newpt = 2 * limit - newpt;
  deltas[i] = -((_random.Next() & 0x00000003) + 2);
 }
 pts[i] = newpt;
}

/**
* Resets the animation data.
*/
private void Reset(int w, int h)
{
 for (int i = 0; i < _animpts.Length; i += 2)
 {
  _animpts[i + 0] = (_random.Next() & 0x00000003) * w / 2;
  _animpts[i + 1] = (_random.Next() & 0x00000003) * h / 2;
  _deltas[i + 0] = (_random.Next() & 0x00000003) * 6 + 4;
  _deltas[i + 1] = (_random.Next() & 0x00000003) * 6 + 4;
  if (_animpts[i + 0] > w / 2)
  {
   _deltas[i + 0] = -_deltas[i + 0];
  }
  if (_animpts[i + 1] > h / 2)
  {
   _deltas[i + 1] = -_deltas[i + 1];
  }
 }
}

/**
 * Sets the points of the path and draws and fills the path.
 */
private void DrawDemo(int w, int h)
{
 for (int i = 0; i < _animpts.Length; i += 2)
 {
  Animate(_animpts, _deltas, i + 0, w);
  Animate(_animpts, _deltas, i + 1, h);
 }
 //Generates the new pata data.
 _path.Reset();
 int[] ctrlpts = _animpts;
 int len = ctrlpts.Length;
 int prevx = ctrlpts[len - 2];
 int prevy = ctrlpts[len - 1];
 int curx = ctrlpts[0];
 int cury = ctrlpts[1];
 int midx = (curx + prevx) / 2;
 int midy = (cury + prevy) / 2;
 _path.MoveTo(midx, midy);
 for (int i = 2; i <= ctrlpts.Length; i += 2)
 {
  int x1 = (curx + midx) / 2;
  int y1 = (cury + midy) / 2;
  prevx = curx;
  prevy = cury;
  if (i < ctrlpts.Length)
  {
   curx = ctrlpts[i + 0];
   cury = ctrlpts[i + 1];
  }
  else
  {
   curx = ctrlpts[0];
   cury = ctrlpts[1];
  }
  midx = (curx + prevx) / 2;
  midy = (cury + prevy) / 2;
  int x2 = (prevx + midx) / 2;
  int y2 = (prevy + midy) / 2;
  _path.CurveTo(x1, y1, x2, y2, midx, midy);
 }
 _path.ClosePath();
 // clear the clipRect area before production

 graphics2D.Clear(Color.White);
 graphics2D.Fill(_brush, _path);

 RefreshBitmap();

}

其中实时更新图像需要CompositionTarget.Rendering事件来处理。CompositionTarget.Rendering += CompositionTargetRendering;

private void CompositionTargetRendering(object sender, EventArgs e)
{
 bmp.Invalidate();
}