Form distance transform based implementation of morphological filter

Erosion and dilation are two basic morphological filters and have been widely used in both academic and industrial fields. When they are used in industry, such as automated visual inspection, their implementation cost especially for large masks is a challenging issue. In this paper, we propose a FDT (form distance transform) method for implementing erosion and dilation for some regular shapes. In this proposed method, the implementation of erosion and dilation is first converted into the computation of its FDT. Then a propagation technique is used to compute the FDT. The computational cost of the new method is independent of mask sizes. In contrast of the direct implementation, if the pixel number in a morphological mask is N, the proposed method reduces the implementation cost from 0(N) to 0(1).