Although the OpenCV documents say:
Mat::at
the variants with a single index (i) can be used to access elements of single-row or single-column 2-dimensional arrays
we can use Mat::at with a single index for usual MxN matrix.
e.g.
cv::Mat m(3,3,CV_32F);
float *p1(m.at<float[3]>(0));
p1[0]=...; p1[1]=...; p1[2]=...;
cv::Vec3f &p2(m.at<cv::Vec3f>(1));
p2[0]=...; p2[1]=...; p2[2]=...;
This way is useful to me. My question is: Is this not a regular way? If OpenCV changes the implementation and restricts the above style, then I would have a trouble.