The paper is devoted to put forward an effective algorithm of image with impulse noise denoising by improving the traditional median filter. The following approaches are developed in this paper. First, in a small area all pixels are separated into signal pixels and suspicious noise pixels making use of the median filtering algorithm based on extremum and median value. Then suspicious noise pixels are further identified as the signal pixels and noise pixels around pixels. If a pixel value is a noise pixel,it will be processed by median filter. A signal pixel will retain the original pixel value. The numerical experiments show that compared with traditional median filter,the details and edge information of the original image are retained when the new algorithm is used. Compared with extremum median filter algorithm, the ratio of peak signal to the noise can increase up to 2. 94 at most. As a result, it is an effective algorithm for image denoising that can eliminate impulse noise in the image effectively.%目的 通过改进传统的中值滤波,研究去除图像中脉冲噪声的有效方法.方法 首先利用极值中值滤波算法将小区域内某像素点确定为信号点和可疑噪声点,然后用该像素点周围信息将可疑噪声点进一步确定为信号点和噪声点；对判断出的噪声点进行中值滤波处理,而对于信号点则保留原来的像素值.结果 数值实验显示应用笔者所提算法对图像进行去噪,能有效避免图像中因纹理等细节的丢失而模糊,得到了相对清晰的图像,去噪后的图像很好地保留了图像的边缘信息,与极值中值滤波算法相比,峰值信噪比值最多能提高2.94.结论 笔者所提算法能有效的区分噪声与边缘信息,可以更多地保留图像的边缘细节信息,减少滤波后造成的图像模糊；提高了峰值信噪比.
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