@Override
public void draw(@NonNull Canvas canvas) {
 int cWidth=canvas.getWidth();
 int cHeight=canvas.getHeight();
 if(rect==null){
 rect=new Rect(cWidth/2-width/2,cHeight/2-height/2,cWidth/2+width/2,cHeight/2+height/2);
 }
 canvas.drawColor(Color.TRANSPARENT);
 Path path=new Path();
 path.addRect(0,0,cWidth,cHeight, Path.Direction.CW);
 cropPath=new Path();
 if(shape==SHAPE_RECT){
 cropPath.addRect(rect.left,rect.top,rect.right,rect.bottom, Path.Direction.CW);
 }else if(shape==SHAPE_CIRCLE){
 cropPath.addCircle(rect.centerX(),rect.centerY(),rect.width()/2, Path.Direction.CW);
 }
 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
 //可以抗锯齿
 path.op(cropPath, Path.Op.DIFFERENCE); 
 canvas.drawPath(path,paint);
 }else{
 //此方法可以去掉锯齿
 //在这里saveLayer然后restoreToCount的操作不能少，否则不会得到想要的效果
 int layerId = canvas.saveLayer(0, 0, cWidth, cHeight, null, Canvas.ALL_SAVE_FLAG);
 canvas.drawPath(path,paint);
 //已经绘制的可以看做为目标图
 paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
 canvas.drawPath(cropPath,paint);
 paint.setXfermode(null);
 canvas.restoreToCount(layerId);
 //裁剪的方式会有锯齿，没找到方法去掉锯齿
 //canvas.clipPath(opPath, Region.Op.DIFFERENCE);
 //canvas.drawRect(0,0,cWidth,cHeight,paint);
 }
}

@Override
public boolean onTouch(View v, MotionEvent event) {

 if(v!=null&&((ImageView) v).getDrawable()!=null){
 ImageView view = (ImageView) v;
 Rect rect=view.getDrawable().getBounds();
 //事件处理
 switch (event.getAction() & MotionEvent.ACTION_MASK) {
 //一个手指按下时，标记为移动模式
 case MotionEvent.ACTION_DOWN:
 matrix.set(view.getImageMatrix());
 savedMatrix.set(matrix);
 start.set(event.getX(), event.getY());
 mode = DRAG;
 break;
 //第二个手指按下时，标记为缩放模式
 case MotionEvent.ACTION_POINTER_DOWN:
 oldDist = distance(event);
 if (oldDist > 10f) {
  savedMatrix.set(matrix);
  midPoint(mid, event);
  mode = ZOOM;
 }
 break;
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_POINTER_UP:
 checkMatrix(rect);
 mode = NONE;
 break;
 //手指移动时，根据当前是移动模式还是缩放模式做相应处理
 case MotionEvent.ACTION_MOVE:
 if (mode == DRAG) {
  matrix.set(savedMatrix);
  matrix.postTranslate(event.getX() - start.x, event.getY()
  - start.y);
 } else if (mode == ZOOM) {
  float newDist = distance(event);
  if (newDist > 10f) {
  matrix.set(savedMatrix);
  float scale = newDist / oldDist;
  matrix.postScale(scale, scale, mid.x, mid.y);
  }
 }
 break;
 }
 view.setImageMatrix(matrix);
 }
 return true;
}

private void checkMatrix(Rect rect){
 if(limit==null&&cropPath!=null){
 limit=cropPath.limit();
 }
 if(limit!=null){
 if(mode==ZOOM){
 matrix.getValues(values);
 if(rect.width()*values[0]<limit.width()){ //当前宽度小于最小宽度
 float scale = limit.width()/(float)rect.width()/values[0];
 matrix.postScale(scale, scale, mid.x, mid.y);
 }
 matrix.getValues(values);
 if(rect.height()*values[4]<limit.height()){ //当前高度小于最小高度
 float scale = limit.height()/(float)rect.height()/values[4];
 matrix.postScale(scale, scale, mid.x, mid.y);
 }
 }
 matrix.getValues(values);
 if(values[2]>=limit.left){
 matrix.postTranslate(limit.left-values[2],0);
 }
 matrix.getValues(values);
 if(values[2]+rect.width()*values[0]<limit.right){
 matrix.postTranslate(limit.right-rect.width()*values[0]-values[2],0);
 }
 matrix.getValues(values);
 if(values[5]>limit.top){
 matrix.postTranslate(0,limit.top-values[5]);
 }
 matrix.getValues(values);
 if(values[5]+rect.height()*values[4]<limit.bottom){
 matrix.postTranslate(0,limit.bottom-rect.height()*values[4]-values[5]);
 }
 }
}

public Bitmap crop(){
 if(imageView!=null&&cropPath!=null){
 if(limit==null){
 limit=cropPath.limit();
 }
 Paint paint=new Paint();
 paint.setAntiAlias(true);
 imageView.setDrawingCacheEnabled(true);
 Bitmap bmp=Bitmap.createBitmap(limit.width(),limit.height(), Bitmap.Config.ARGB_8888);
 Canvas canvas=new Canvas(bmp);
 canvas.drawColor(Color.TRANSPARENT);
 int lId=canvas.saveLayer(0,0,limit.width(),limit.height(),null,Canvas.ALL_SAVE_FLAG);
 Path path=new Path();
 path.addPath(cropPath.path(),-limit.left,-limit.top);
 canvas.drawPath(path,paint);
 paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
 canvas.drawBitmap(imageView.getDrawingCache(),-limit.left,-limit.top,paint);
 paint.setXfermode(null);
 canvas.restoreToCount(lId);
 imageView.setDrawingCacheEnabled(false);
 return bmp;
 }
 return null;
}

public String cropAndSave(String path) throws IOException {
 Bitmap bmp=crop();
 if(bmp==null)return null;
 File file=new File(path);
 if(!file.getParentFile().exists()){
 boolean b=file.mkdirs();
 if(!b)return null;
 }
 if(file.exists()){
 boolean c=file.delete();
 if(!c)return null;
 }
 FileOutputStream fos=new FileOutputStream(file);
 bmp.compress(Bitmap.CompressFormat.PNG,100,fos);
 fos.flush();
 fos.close();
 bmp.recycle();
 return file.getAbsolutePath();
}