Can I determine the number of channels in cv::Mat Opencv

Call Mat.channels() :

cv::Mat img(1,1,CV_8U,cvScalar(0));
std::cout<<img.channels();

Output:

1

which is the number of channels.

Also, try:

std::cout<<img.type();

Output:

0

which belongs to CV_8U (look here at line 542). Study file types_c.h for each define.