Android编程实现扭曲图像的绘制功能示例

private static Bitmap bitmap;
private MyView myView;
private int angle = 0;         // 圆形轨迹当前的角度
private Handler handler = new Handler()
{
   public void handleMessage(Message msg)
   {
     switch (msg.what)
     {
       case 1:
         Random random = new Random();
         // 计算图形中心点坐标
         int centerX = bitmap.getWidth() / 2;
         int centerY = bitmap.getHeight() / 2;
         double radian = Math.toRadians((double) angle);
         // 通过圆心坐标、半径和当前角度计算当前圆周的某点横坐标
         int currentX = (int) (centerX + 100 * Math.cos(radian));
         // 通过圆心坐标、半径和当前角度计算当前圆周的某点纵坐标
         int currentY = (int) (centerY + 100 * Math.sin(radian));
         // 重绘View，并在圆周的某一点扭曲图像
         myView.mess(currentX, currentY);
         angle += 2;
         if (angle > 360)
           angle = 0;
         break;
     }
     super.handleMessage(msg);
   }
};
private TimerTask timerTask = new TimerTask()
{
   public void run()
   {
     Message message = new Message();
     message.what = 1;
     handler.sendMessage(message);
   }

private static class MyView extends View
{
    private static final int WIDTH = 20;
    private static final int HEIGHT = 20;
    private static final int COUNT = (WIDTH + 1) * (HEIGHT + 1);
    private final float[] verts = new float[COUNT * 2];
    private final float[] orig = new float[COUNT * 2];
    private final Matrix matrix = new Matrix();
    private final Matrix m = new Matrix();
    // 设置verts数组的值
    private static void setXY(float[] array, int index, float x, float y)
    {
      array[index * 2 + 0] = x;
      array[index * 2 + 1] = y;
    }
    public MyView(Context context)
    {
      super(context);
      setFocusable(true);
      bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
      float w = bitmap.getWidth();
      float h = bitmap.getHeight();
      int index = 0;
      // 生成verts和orig数组的初始值，这两个数组的值是一样的，只是在扭曲的过程中需要修改verts
      // 的值，而修改verts的值要将原始的值保留在orig数组中
      for (int y = 0; y <= HEIGHT; y++)
      {
        float fy = h * y / HEIGHT;
        for (int x = 0; x <= WIDTH; x++)
        {
          float fx = w * x / WIDTH;
          setXY(verts, index, fx, fy);
          setXY(orig, index, fx, fy);
          index += 1;
        }
      }
      matrix.setTranslate(10, 10);
      setBackgroundColor(Color.WHITE);
    }
    @Override
    protected void onDraw(Canvas canvas)
    {
      canvas.concat(matrix);
      canvas.drawBitmapMesh(bitmap, WIDTH, HEIGHT, verts, 0, null, 0,null);
    }
    // 用于扭曲图像的方法，在该方法中根据当前扭曲的点（扭曲区域的中心点），也就是cx和cy参数，
    // 来不断变化verts数组中的坐标值
    private void warp(float cx, float cy)
    {
      final float K = 100000;  // 该值越大，扭曲得越严重（扭曲的范围越大）
      float[] src = orig;
      float[] dst = verts;
      // 按一定的数学规则生成verts数组中的元素值
      for (int i = 0; i < COUNT * 2; i += 2)
      {
        float x = src[i + 0];
        float y = src[i + 1];
        float dx = cx - x;
        float dy = cy - y;
        float dd = dx * dx + dy * dy;
        float d = FloatMath.sqrt(dd);
        float pull = K / ((float) (dd *d));
        if (pull >= 1)
        {
          dst[i + 0] = cx;
          dst[i + 1] = cy;
        }
        else
        {
          dst[i + 0] = x + dx * pull;
          dst[i + 1] = y + dy * pull;
        }
      }
    }
    // 用于MyView外部控制图像扭曲的方法。该方法在handleMessage方法中被调用
    public void mess(int x, int y)
    {
      float[] pt ={ x, y };
      m.mapPoints(pt);
      // 重新生成verts数组的值
      warp(pt[0], pt[1]);
      invalidate();
    }
  }
}

protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    myView = new MyView(this);
    setContentView(myView);
    Timer timer = new Timer();
    // 开始定时器
    timer.schedule(timerTask, 0, 100);
}