android开发分享Android自定义橡皮擦效果

  public class picfingertotest extends view {      private paint paint;    private bitmap decoderesourcesrc;    private bitmap createbitmapdst;    // 手指路径，使用贝塞尔路线    private path path;    private float perx;    private float pery;      public picfingertotest(context context, attributeset attrs) {      super(context, attrs);      // 1、设置禁用硬件设置      setlayertype(view.layer_type_software, null);        // 2、设置手指画笔      paint = new paint();      paint.setantialias(true);      paint.setcolor(color.red);      paint.setstyle(paint.style.stroke);      paint.setstrokewidth(45);        // 3、生成图像手指源目标      // 源      decoderesourcesrc = bitmapfactory.decoderesource(getresources(), r.drawable.welcome, null);      // 目标      createbitmapdst = bitmap.createbitmap(decoderesourcesrc.getwidth(), decoderesourcesrc.getheight(),          config.argb_8888);      path = new path();      }      @override    protected void ondraw(canvas canvas) {      super.ondraw(canvas);      // 分层绘制      int savelayer = canvas.savelayer(0, 0, getwidth(), getheight(), null,canvas.all_save_flag);        // 把手指轨迹划到目标路径上      canvas canvas2 = new canvas(createbitmapdst);      canvas2.drawpath(path, paint);        // 把目标图像画到画布上      canvas.drawbitmap(createbitmapdst, 0, 0, paint);        // 计算源图像区域        paint.setxfermode(new porterduffxfermode(mode.src_out));      canvas.drawbitmap(decoderesourcesrc, 0, 0, paint);        paint.setxfermode(null);      canvas.restoretocount(savelayer);      }      //使用贝塞尔曲线，使折线过度圆滑    @override    public boolean ontouchevent(motionevent event) {        switch (event.getaction()) {      // 记录手指触摸的初始化位置      case motionevent.action_down:          path.moveto(event.getx(), event.gety());          perx = event.getx();        pery = event.gety();          return true;        case motionevent.action_move:          float endx = (perx + event.getx()) / 2;        float endy = (pery + event.gety()) / 2;          path.quadto(perx, pery, endx, endy);        perx = event.getx();        pery = event.gety();        postinvalidate();          break;      case motionevent.action_up:          break;        default:        break;      }        return super.ontouchevent(event);    }    }    

  public void oncreate() {    //底边图片    imageview ivtop = (imageview) findviewbyid(r.id.iv_top);       options opts = new options(); //图片加载器，用于配置一些缩放比例，和像素单位    opts.insamplesize = 2; //制定加载器把原图片的宽高缩放到2/1的效果加载    //获得外层图片,decoderesource方法默认获得的像素单位是rgb(red,green,blue),argb(alpha,red,green,blue)    bitmap topimage = bitmapfactory.decoderesources( getresource(),r.drawable.top, opts);       //创建一张空白图片，并且把图片想读单位指定为:argb    bitmap blank = bitmap.createbitmap(topimage.getwidth(), topimage.getheight, config.argb_4444);       //把上边的topimage画到空白图片上    canvas canvas = new canvas(blank);    //把topimage画到空白图片上但是像素单位变成argb()    canvas.drawbitmap(topimage, 0, 0, null);    ivtop.setimagebitmap(blank);  }     class myontouchlistoner implements ontouchlistener {       @override pulic boolean ontouch(view v, motionevent event) {      //是否是移动的事件      if (event.getaction() == motionevent.action_move) {        //获得按下坐标        int x = (int) event.getx();        int y = (int) event.gety();           for (int i = x - 10; i < x + 10; i++) {          for (int j = y - 10; j < y + 10; j++) {            //防止超出边界            if (j >= 0 && blank.getheight() && i >= 0 && i < blank.getwidth()) {              blank.setpixel(i, j, color.transparent);            }          }        }        //修改后的图片设置给imageview        ivtop.setimagebitmap(blank);      }         return true; //true 消耗掉这次触摸事件.false 不消耗    }     }