Mat me = (Mat_<float>(4, 4) << 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1);
Mat meinv = me.inv();
cout << "me=\n" << me << endl;
cout << "meinv=" << endl << meinv << endl << endl;
int nonZerosNum = countNonZero(me);
cout << "me = " << endl << me << endl;
cout << "me中非零元素的个数=" << nonZerosNum << endl;
//均值和方差
Mat mean;
Mat stddev(1,1,CV_8UC1);
meanStdDev(me, mean, stddev);
Mat_<uchar>img = stddev;//Mat_是Mat的派生类.
//优点：Mat_对象访问元素时不再需要指定元素类型；而Mat类型对象需要在<>中指定元素类型，如用img.at<类型>(i,j)。
img(0,0) = 100;
cout << "mean=" << mean << endl << endl;
cout << "stddev=" << stddev << endl << endl;
cout << "stddev=" <<int(img(0,0)) << endl << endl;原文：http://blog.51cto.com/joekeji/2326922