The structuring element is normally represented by a binary or int32 matrix that by convention the position of the origin [0,0] is at the center of the matrix. The structuring elements can be flat, represented by a binary matrix or non-flat, represented by an uint32 matrix. Sometimes, the structuring element can be represented by an internal data structure so that the best way to visualize a structuring element is by calling the function mmseshow which converts the structuring element to a matrix with the above conventions.