Median filter on FPGAs

Median filters have been shown to be effective in removing impulsive noise from images. This paper proposes three different directional median filter implementations on FPGA. The techniques are capable of performing median filtering operations for four different directions simultaneously. These implementations are extensions to an existing cumulative histogram-based median filtering technique. Yet, directional processing was not addressed in previous work. Directional median filters process images along the direction of the filtering window, and have been shown to be more effective in removing impulsive noise compared to traditional median filters. All techniques aimed to decrease processing time, while reducing the resource utilization on hardware. Experimental results confirmed that all three techniques are synthesizable and implementable on Xilinx Virtex 5. There is a trade-off between resource utilization and processing time among the three techniques.