1.The idea is that each Mat object has its own header, however the matrix may be shared between two instance of them by having their matrix pointers point to the same address. Moreover, the copy operators will only copy the headers and the pointer to the large matrix, not the data itself.
Mat B(A) C=A
2.Sometimes you will want to copy the matrix itself too, so OpenCV provides the cv::Mat::clone() and cv::Mat::copyTo() functions.
Mat F = A.clone(); Mat G; A.copyTo(G);
3.OpenCV standard display system composes colors using the BGR color space
4.g(x)=αf(x)+β. The parameters α>0 and β are often called the gain and bias parameters; sometimes these parameters are said to control contrast and brightness respectively. Gamma correction can be used to correct the brightness of an image by using a non linear transformation between the input values and the mapped output values:
5.RGB(255,255,255)是白色
6.copyTo的掩模必须是8U但可以使多通道的
来源：https://www.cnblogs.com/zhujiangning/p/11526569.html