Mat_<_Tp>::end() iterator pointer yields wrong address for subregioned matrices. (Bug #72)

Hi,

I need to get a matrix header for a subregion of a matrix. I'm doing something like

Mat_<_Tp> sub = Mat_<_Tp>(roi.height, roi.width, &org_mat(roi.y, roi.x), org_mat.cols * sizeof(_Tp));

which works ok. That is... until I start to use an iterator:

Mat_<_Tp>::iterator it = sub.begin();
Mat_<_Tp>::iterator itend = sub.end();
while(it != itend) {
  // Do something with *it
  it++;
}

which fails, because 'it' is never equal to 'itend'. As far as I can see, it is line 499 and 485 in cxmat.hpp that should be changed from

it.ptr = it.sliceEnd = (_Tp*)(data + step*(rows-1)) + cols;

it.ptr = it.sliceEnd = (_Tp*)(data + step*rows);

No, I have not tested this extensively, but my code works if I insert

itend.ptr = itend.sliceEnd = (_Tp*)(sub.data + sub.step*sub.rows);

I hope that someone with a deeper insight to OpenCV will take a look at this and check that my solution proposal will work with the rest of the library.

Ps.: For now I (and other users in the same position) can use the constellation "while(it < itend)" instead for own loops.