In the example bellow we show the composition. The initial structuring element will be "an isolated point", ie, { 000 010 000 } (seen as a 3X3 matrix where each block is one of its rows), the final one will be { 010 101 010 } or "a 4-connected hole". The first picture is the input image, the second one its dilation, the third one the erosion of the input image and the fourth one the inversion of the previos one (erosion). The last image is the supremum of the dilation and the anti-erosion .