As reported previously, porous diamond membranes can be fabricated using a method based on growing diamond on a patterned silicon surface. Protrusions on the silicon surface act as molds for forming the pores on the diamond films. This method leads to a non-negligible pore size non-uniformity. The present work is concerned with identifying the process that accounts for this, so as to minimize its effects. The approach developed here is based on the digital processing of the scanning electron microscope (SEM) images obtained from selected pores in five different membranes.