iOS Crop Image From Custom Overlay in Camera Mode

Question

I m using UIImagePickerController and customize the "cameraOverlay".

    - (UIImagePickerController *)imagePickerCtrl
    {
        if (_imagePickerCtrl)
        {
            return _imagePickerCtrl;
        }
        _imagePickerCtrl = [[UIImagePickerController alloc] init];
        _imagePickerCtrl.sourceType = UIImagePickerControllerSourceTypeCamera;
        _imagePickerCtrl.showsCameraControls = NO;
        _imagePickerCtrl.delegate = self;
        CameraOverlayView *overlay = [[CameraOverlayView alloc] initWithFrame:(CGRect){0, 0, SCREENWIDTH, SCREENHEIGHT} innerRectSize:CGSizeMake(SCREENWIDTH - 10 * 2, (SCREENWIDTH - 10 * 2) * 0.618) innerCornerRadius:20.0];
        _imagePickerCtrl.cameraOverlayView = overlay;
        @WeakObj(self);
        [overlay setBlock:^(NSInteger tag) {

            if (!tag)//取消
            {
                [weakself.imagePickerCtrl dismissViewControllerAnimated:YES completion:nil];
            }
            else//照相
            {
                [weakself.imagePickerCtrl takePicture];
            }

        }];
        return _imagePickerCtrl;

}

Here is the screen shot:

My problem is I don't know how to get the correct frame of the cropped image.() Here is the code I used to crop image:

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info
{
    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
    CameraOverlayView *overlay = picker.cameraOverlayView;
//    NSLog(@"%@", NSStringFromCGRect(overlay.cropFrame));
    UIImage *croppedImage = [self cropImage:[image fixOrientation] cropFrame:overlay.cropFrame];// the fixOrientation is a category from someone else.
    if (_block)
    {
        _block(croppedImage);
    }
    [picker dismissViewControllerAnimated:YES completion:nil];
}

- (UIImage *)cropImage:(UIImage *)originalImage cropFrame:(CGRect)cropFrame
{
    CGImageRef resultImageRef = CGImageCreateWithImageInRect(originalImage.CGImage, cropFrame);//I m pretty sure the key is got the The crop frame. 

    UIImage *newImage = [[UIImage alloc] initWithCGImage:resultImageRef scale:1.0 orientation:originalImage.imageOrientation];

    return newImage;
}