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  } }