关于opencv的一个问题，跪求解答

#include

#include

#include

using namespace cv;

int main()
{

Mat img = imread("pp.jpg");
Mat logo = imread("z.jpg");
Mat imgROI;
imgROI = img(Rect(200,300,logo.cols,logo.rows));
addWeighted(imgROI,0.5,logo,0.5,0,imgROI);

namedWindow("叠加效果图");
imshow("叠加效果图", img);

imwrite("shiyan.jpg",img);
waitKey();
return 0;

}

运行出错，如图所示。如果屏蔽imwrite图像可以正确显示，百思不得其解，希望大家帮帮忙