“…Both the dilation and the erosion are basic operations in mathematical morphology and are part of conventional software packages such as IDL and MATLAB. Mathematically, the dilation of f ( x , y ) by a structuring element B , denoted as f ⊕ B , is equivalent to a local‐maximum operator [e.g., González et al ., ]: where ( x , y ) denotes the set of discrete spatial coordinates and D ( B ) is the domain of the structuring element B , i.e., the pixels from the neighborhood defined by B , where the maximum is evaluated. Similarly, the erosion of f ( x , y ) by a structuring element B , denoted as f ⊖ B , is equivalent to a local‐minimum operator: Combining equations and gives the morphological closing of f ( x , y ) by a structuring element B , denoted as C B ( f ): …”