Band-Pass ε-Filter for Edge Enhancement and Noise Removal

A band-pass bilateral filter is an improved variant of a bilateral filter that does not have low-pass characteristics but has band-pass characteristics. Unfortunately, its computation time is relatively large since all pixels are subjected to Gaussian calculation. To solve this problem, we pay attention to a nonlinear filter called e-filter and propose an advanced E-filter labeled band-pass epsilon-filter. As epsilon-filter has low-pass characteristics due to spatial filtering, it does not enhance the image contrast. On the other hand, band-pass E-filter does not have low-pass characteristics but has band-pass characteristics to enhance the image contrast around edges unlike epsilon-filter. The filter works not only as a noise reduction filter but also as an edge detection filter depending on the filter setting. Due to its simple design, the calculation cost is relatively small compared to the band-pass bilateral filter. To show the effectiveness of the proposed method, we report the results of some comparison experiments on the filter characteristics and computational cost.