基于opencv计算星云图像的面积与周长

清疚 2022-06-14 06:39 180阅读 0赞

![Center][]

需求：以上图像是太空望远镜的星云图像，要求通过opencv计算出星云的面积与周长。

解决思路：通过二值分割+图像形态学+轮廓提取。

代码如下

#include <opencv2/opencv.hpp>
    #include <iostream>
    #include <math.h>
    
    using namespace cv;
    using namespace std;
    
    int main()
    {
        Mat src_image = imread("1.jpg");
        if(!src_image.data)
        {
            cout << "src image load failed!" << endl;
            return -1;
        }
        namedWindow("src image", WINDOW_NORMAL);
        imshow("src image", src_image);
    
        /*此处高斯去燥有助于后面二值化处理的效果*/
        Mat blur_image;
        GaussianBlur(src_image, blur_image, Size(15, 15), 0, 0);
        imshow("GaussianBlur", blur_image);
    
        /*灰度变换与二值化*/
        Mat gray_image, binary_image;
        cvtColor(blur_image, gray_image, COLOR_BGR2GRAY);
        threshold(gray_image, binary_image, 0, 255, THRESH_BINARY|THRESH_TRIANGLE);
        imshow("binary", binary_image);
    
        /*形态学闭操作*/
        Mat morph_image;
        Mat kernel = getStructuringElement(MORPH_RECT, Size(3, 3), Point(-1, -1));
        morphologyEx(binary_image, morph_image, MORPH_CLOSE, kernel, Point(-1, -1), 2);
        imshow("morphology", morph_image);
    
        /*查找外轮廓*/
        vector< vector<Point> > contours;
        vector<Vec4i> hireachy;
        findContours(morph_image, contours, hireachy, CV_RETR_EXTERNAL, CHAIN_APPROX_SIMPLE, Point());
        Mat result_image = Mat::zeros(src_image.size(), CV_8UC3);
        for(size_t t = 0; t < contours.size(); t++)
        {
            /*过滤掉小的干扰轮廓*/
            Rect rect = boundingRect(contours[t]);
            if(rect.width < src_image.cols/2)
                continue;
            if(rect.width > (src_image.cols - 20))
                continue;
    
            /*计算面积与周长*/
            double area = contourArea(contours[t]);
            double len = arcLength(contours[t], true);
    
            drawContours(result_image, contours, static_cast<int>(t), Scalar(0, 0, 255), 1, 8, hireachy);
            cout << "area of start cloud: " << area << endl;
            cout << "len of start cloud: " << len << endl;
        }
    
        imshow("result image", result_image);
    
        waitKey(0);
    
        return 0;
    }

图像处理后的提取的轮廓图如下

![Center 1][]

根据以上的轮廓图可以计算出星云的面积与周长，详见以上代码。

[Center]: /images/20220614/876c67bd4f254081bd508fddc4dbb441.png
[Center 1]: /images/20220614/9876acbfc63843fc97af9649c0a2264d.png