OpenCV:如何删除不需要的 Blob 或如何将想要的部分复制到空图像中？

Question

从下图中，我如何找到结果图像？



此处显示的图像是阈值图像。我尝试过使用形态运算符，但它们甚至删除了我想要的 blob。我该如何解决这个问题？
有什么提示吗？

以下是我有兴趣获取/查找的结果图像:

import cv2
diff = cv2.imread('Image.png',0)
ret, thresh = cv2.threshold(diff, 12.5, 255, cv2.THRESH_BINARY)
thresh = cv2.dilate(thresh, None, iterations = 1)
cv2.imshow('img', thresh) # This is the  first picture I have shown
cv2.waitKey(0)

Answer 1

你已经到了那里，你现在需要做的就是找到 Blob ，添加一些轮廓并找到最大的。简单的!以下是 C++ 中的代码，请自行决定如何将其转换为 Python:

cv::Mat mat = imread("g0cVU.png");
    Mat origImage = mat;
    Mat canny_output = mat;
    vector<vector<Point> > contours;
    vector<Vec4i> hierarchy;
    cv::Mat greyMat, colorMat;
    cv::cvtColor(mat, greyMat, CV_BGR2GRAY);
    int thresh = 100;
    RNG rng(12345);
    ///// Detect edges using canny
    Canny(greyMat, canny_output, thresh, thresh * 2, 3);
    /// Find contours
    findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));
    int largest_area = 0;
    int largest_contour_index = 0;
    Rect bounding_rect;
    /// Draw contours
    Mat drawing = Mat::zeros(canny_output.size(), CV_8UC3);
    for (int i = 0; i< contours.size(); i++)
    {
        Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
        drawContours(drawing, contours, i, color, 2, 8, hierarchy, 0, Point());
        double a=contourArea( contours[i],false);  //  Find the area of contour
       if(a>largest_area){
       largest_area=a;
       largest_contour_index=i;                //Store the index of largest contour
       bounding_rect=boundingRect(contours[i]); // Find the bounding rectangle for biggest contour
       }
    }
    rectangle(origImage, bounding_rect, Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255)),2);
    /// Show in a window
    namedWindow("Contours", CV_WINDOW_AUTOSIZE);
    imshow("Contours", drawing);

    cv::namedWindow("img");
    cv::imshow("mat", mat);
    cv::imshow("mat", origImage);
    cv::imshow("mat123", drawing);
    cv::waitKey(0);

这给出了这个结果:





您可以在底部图像中看到最大的等高线周围绘制了一个棕色矩形。

o 显然，一旦您拥有最大的 blob(或您认为“正确的 blob”)，您就可以将其他所有内容设置为黑色，这非常简单。