1. 中值滤波原理

中值滤波算法以某像素的领域图像区域中的像素值的排序为基础，将像素领域内灰度的中值代替该像素的值[1]；

如：以3*3的领域为例求中值滤波中像素5的值

1. int pixel[9]中存储像素1，像素2…像素9的值；
2. 对数组pixel[9]进行排序操作；
3. 像素5的值即为数组pixel[9]的中值pixel[4]。

中值滤波对处理椒盐噪声非常有效。

2. C++代码实现

void medianFilter (unsigned char* corrupted, unsigned char* smooth, int width, int height)  
{  
      
    memcpy ( smooth, corrupted, width*height*sizeof(unsigned char) );  
    for (int j=1;j<height-1;j++)  
    {  
        for (int i=1;i<width-1;i++)  
        {  
            int k = 0;  
            unsigned char window[9];  
            for (int jj = j - 1; jj < j + 2; ++jj)  
                for (int ii = i - 1; ii < i + 2; ++ii)  
                    window[k++] = corrupted[jj * width + ii];  
            //   Order elements (only half of them)  
            for (int m = 0; m < 5; ++m)  
            {  
                int min = m;  
                for (int n = m + 1; n < 9; ++n)  
                    if (window[n] < window[min])  
                        min = n;  
                //   Put found minimum element in its place  
                unsigned char temp = window[m];  
                window[m] = window[min];  
                window[min] = temp;  
            }  
            smooth[ j*width+i ] = window[4];  
        }  
    }  
}  

3. 最后