Android 倒影算法的实现代码

public class mirrorview extends view {
 paint m_paint;
 int m_nshadowh;
 drawable m_dw;
 bitmap m_bitmap;
 //xxxx
 matrix mmatrix;
 int shadowheight;
 public mirrorview(context context, bitmap bitmap) {
  super(context);
  m_bitmap = bitmap;
  _init();
  // todo auto-generated constructor stub
 }
 private void _init() {
  //m_dw = new bitmapdrawable(bitmapfactory.decoderesource(getresources(),  r.drawable.icon));
  m_dw = new bitmapdrawable(m_bitmap);
  m_dw.setbounds(0,0,m_dw.getintrinsicwidth(),m_dw.getintrinsicheight());
  m_nshadowh = m_dw.getintrinsicheight()/1;
  m_paint = new paint(paint.anti_alias_flag);
  lineargradient lg = new lineargradient(0, 0, 0, m_nshadowh, 0xb0ffffff, 0x00000000, shader.tilemode.clamp);
  m_paint.setshader(lg);
  m_paint.setxfermode(new porterduffxfermode(porterduff.mode.multiply)); 
  //xxxx
  mmatrix = new matrix();
 }
 @override
 public void ondraw(canvas canvas) {
  super.ondraw(canvas);
  int nx = 0;
  int ny = 0;
  _drawnormalimg(canvas, nx, ny);
  _drawmirror(canvas, nx, ny);
 }
 private void _drawnormalimg(canvas canvas, int nx, int ny) {
  canvas.save(canvas.matrix_save_flag);
  canvas.translate(nx, ny);
  m_dw.draw(canvas);
  canvas.restore();
 }
 private void _drawmirror(canvas canvas, int nx, int ny) {
  int nw = m_dw.getintrinsicwidth();
  int nh = m_dw.getintrinsicheight();
//  u.dout("nw="+nw+",nh="+nh);
  //xxxx
  shadowheight=nh/2;
  //xxxx
  float[] src={0, nh, nw, nh, nw,nh - m_nshadowh, 0, nh - m_nshadowh};
  float[] dst={ 0, nh, nw, nh,nw, shadowheight, 0, shadowheight };
  //xxxx
  canvas.save();
  mmatrix.setpolytopoly(src, 0, dst, 0, src.length >> 1);
  canvas.concat(mmatrix);
  //draw mirror image 
  canvas.save(canvas.matrix_save_flag);
  canvas.scale(1.0f, -1.0f);
  canvas.translate(nx, -(ny + nh * 2));
  canvas.cliprect(0, nh, nw, nh - m_nshadowh);
  m_dw.draw(canvas);
  canvas.restore();
  //draw mask 
  canvas.save();
  canvas.translate(nx, ny + nh);
  canvas.drawrect(0, 0, nw, m_nshadowh, m_paint);
  canvas.restore();
  //xxxx
  canvas.restore();
 }
}