OpenCv 023---中值模糊

1 前备知识　　

  中值滤波本质上是统计排序滤波器的一种，中值滤波对图像特定噪声类型（椒盐噪声）会取得比较好的去噪效果，也是常见的图像去噪声与增强的方法之一，相对的还有最小值滤波，最大值滤波。中值滤波也是窗口在图像上移动，其覆盖的对应ROI区域下，所有像素值排序，取中值作为中心像素点的输出值，与均值滤波相对比，该滤波方法不用做卷积(点乘相加)。具体操作方法如下图：

2 所用到的主要OpenCv API

/** @brief Blurs an image using the median filter.
The function smoothes an image using the median filter with the \f$\texttt{ksize} \times
\texttt{ksize}\f$ aperture. Each channel of a multi-channel image is processed independently.
In-place operation is supported.
@note The median filter uses #BORDER_REPLICATE internally to cope with border pixels, see #BorderTypes
@param src input 1-, 3-, or 4-channel image; when ksize is 3 or 5, the image depth should be
CV_8U, CV_16U, or CV_32F, for larger aperture sizes, it can only be CV_8U.
@param dst destination array of the same size and type as src.
@param ksize aperture linear size; it must be odd and greater than 1, for example: 3, 5, 7 ...
@sa  bilateralFilter, blur, boxFilter, GaussianBlur
 */
CV_EXPORTS_W void medianBlur( InputArray src, OutputArray dst, int ksize );

3 程序代码

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main(int artc, char** argv) {
    Mat src = imread("images/sp_noise.png");
    if (src.empty()) {
        printf("could not load image...\n");
        return -1;
    }
    namedWindow("input", CV_WINDOW_AUTOSIZE);
    imshow("input", src);

    Mat dst;
    medianBlur(src, dst, 5);//5为滤波使用的kernel size，必须为奇数
    imshow("medianblur ksize=5", dst);

    waitKey(0);
    return 0;
}

4 运行结果

5 扩展及注意事项

none

6*目前只做大概了解，知道有这一算法，后续具体使用再做具体分析