代码如下： 

 #include <opencv2/opencv.hpp>
int main(int argc, char** argv) {
    cv::Mat img1, img2;
    cv::namedWindow("Example1", cv::WINDOW_AUTOSIZE);
    cv::namedWindow("Example2", cv::WINDOW_AUTOSIZE);
    img1 = cv::imread(argv[1]);
    cv::imshow("Example1", img1);
    cv::pyrDown(img1, img2);
    cv::imshow("Example2", img2);
    cv::waitKey(0);
    return 0;
};

执行的时候报错：

OpenCV Error: Assertion failed (size.width>0 && size.height>0) in cv::imshow, file C:\builds\master_PackSlave-win64-vc12-shared\opencv\modules\highgui\src\window.cpp, line 271

解决办法：opencv-world300lib 放在opencv-ts300lib的后面

参考：

https://www.cnblogs.com/siberianhusky/p/13034034.html