Optimizationg And Realization Of Median Filtering Algorithm In Image Processing

With the continuous development of computer technology, digital image processing technology has increasingly gained more attentions and is more widely applied. Many new theories and methods have been emerged continuously. Image signal is often interfered by many kinds of noises when it is produced, transmitted and recorded in practical application processes because of the communication channels and equipment, environmental factors such as interference. The original signal in digital image is always accompanied by noises The quality of image must be improved by filtering technology before edge detection, image segmentation, feature extraction, pattern recognition and so on. Image filtering is expected to both reduce the noise and keep the delicate details. But it is difficult to design such a good filter because of the overlapping of noise and image details. Image filtering is a very important and hot research field in image processing.Firstly, this thesis discusses some fundamental concepts in digital image processing and median filtering. Secondly, to resolve the contradiction of removing noise and holding image details in median filtering simultaneously, this thesis presents two modified algorithms in different ways. One is direction based adaptive multistage median filtering. The author hopes the details can be protected better through judging the directions of the details. The other is extremum median filtering based on threshold and ratio. The author hopes the details can be kept better by classifying noise more accurately and this algorithm stands the noise brought in our real life better, not only some models in theory.