opencv - Finding the size in bytes of cv::Mat -

opencv - Finding the size in bytes of cv::Mat -

i'm using opencv cv::mat objects, , need know number of bytes matrix occupies in order pass low-level c api. seems opencv's api doesn't have method returns number of bytes matrix uses, , have raw uchar *data public fellow member no fellow member contains actual size.

how can 1 find cv::mat size in bytes?

the mutual reply calculate total number of elements in matrix , multiply size of each element, this:

// given cv::mat named mat. size_t sizeinbytes = mat.total() * mat.elemsize();

this work in conventional scenarios, matrix allocated contiguous chunk in memory.

but consider case scheme has alignment constraint on number of bytes per row in matrix. in case, if mat.cols * mat.elemsize() not aligned, mat.iscontinuous() false, , previous size calculation wrong, since mat.elemsize() have same number of elements, although buffer larger!

the right answer, then, find size of each matrix row in bytes, , multiply number of rows:

size_t sizeinbytes = mat.step[0] * mat.rows;

read more step here.

opencv