Abstract: Median filtering is an effective method to reduce salt and pepper noise in image processing. Its core is to calculate the median of all pixels in the current filtering window. Median filtering is stable. When the pixels of an image are changed, the calculation results of median filtering will not be affected even if the changed value is large. After the filtering window traverses the whole image, the median filtering calculation of the whole image is completed. The key of the median filtering algorithm is to define the optimal median algorithm, which can obtain the median in the shortest time. In this regard, an adaptive median algorithm is proposed and implemented, which can automatically select the median algorithm with the best performance according to the filtering window radius and data type, and use ARM NEON instruction set for optimization and acceleration. Experimental results show that the proposed adaptive median filtering algorithm significantly outperforms OpenCV, and the  average performance is improved by 20%.  

Key words: median filtering, median algorithm, ARM instruction set