如何裁剪圆形（找到与霍夫变换）在OpenCV？ [英] How to crop circles (found with Hough Transform) in OpenCV?

问题描述

我使用页。它工作得很好，我得到一个我想要的圈子。所有我的图像只有一个圆，我修改了 HoughCircles（）的参数，使得代码只返回一个圆。

I'm using the code from the page. It works very well and I get a circle that I am looking for. All my image have only 1 circle and I have modified parameters of HoughCircles() such that the code returns only 1 circle.

如何裁剪原始图片，使新图片只有圆形（和其中的区域），并将新图片另存为JPEG或PNG文件？

How can I crop my original image so that the new image has only the circle (and area within it) and save the new image as a JPEG or PNG file?

根据原始代码，圈子中心由

Based upon original code, the center of the circle is given by

(cvRound(circles[1][0]), cvRound(circles[1][1]));

，半径由

cvRound(circles[1][2]);

推荐答案

您应该使用 copyTo 使用遮罩来检索圆圈内的图像部分，然后您可以

You should use copyTo with a mask to retrieve the part of image inside the circle, and then you can crop according to the bounding box of the circle.

您可以使用 imwrite 。

这个小例子可以让你开始。

This small example should get you started.

#include "opencv2/opencv.hpp"
using namespace cv;

int main()
{
    // Your initial image
    Mat3b img = imread("path_to_image");

    // Your Hough circle
    Vec3f circ(100,50,30); // Some dummy values for now

    // Draw the mask: white circle on black background
    Mat1b mask(img.size(), uchar(0));
    circle(mask, Point(circ[0], circ[1]), circ[2], Scalar(255), CV_FILLED);

    // Compute the bounding box
    Rect bbox(circ[0] - circ[2], circ[1] - circ[2], 2 * circ[2], 2 * circ[2]);

    // Create a black image
    Mat3b res(img.size(), Vec3b(0,0,0));

    // Copy only the image under the white circle to black image
    img.copyTo(res, mask);

    // Crop according to the roi
    res = res(bbox);

    // Save the image
    imwrite("filename.png", res);

    // Show your result
    imshow("Result", res);
    waitKey();

    return 0;
}

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