opencv c ++查找轮廓的内切圆 [英] opencv c++ find inscribing circle of a contour

问题描述

我想找到轮廓的最大内切圆.

我用cv::findContours检测到轮廓，并以vector<Point>的形式存在.

I have detected the contour with cv::findContours and it is there as a vector<Point>.

我知道如何检测最小封闭圆(cv::minEnclosingCircle)，但不知道如何获取最大封闭圆.该怎么做?

I know how to detect the minimum enclosing circle (cv::minEnclosingCircle), but not how to get the maximum inclosing circle. How to do this?

问题2:如何使刻划和外接圆以质心为中心?

Question2: How do i get the inscribing and circumscribing circles centered on the center of mass?

为澄清起见，我尝试描述这些圆圈的含义:

For clarification, i try to describe, what i mean with these circels:

1. 最小包围圈:从外部触摸物体，中心位置无所谓，最小面积.
2. 外接圆:从外部触摸对象，中心位置位于对象的质心上，最小面积.
3. 最大闭合圆:从内部触摸物体，中心位置无所谓，最大面积.
4. 内切圆:从内部触摸对象，对象的质心的中心位置，最大面积.

1. min enclosing circle: touching object from outside, center position doesn't matter, minimum area.
2. circumscribing circle: touching object from outside, center position on the center of mass of the object, minimum area.
3. max inclosing circle: touching object from inside, center position doesn't matter, maximum area.
4. inscribing circle: touching object from inside, center position on the center of mass of the object, maximum area.

推荐答案

您可以:

1)从轮廓创建蒙版

2)计算蒙版上的distanceTransform

3)最大值是半径，位置是中心

3) The highest value is the radius, its position is the center

代码:

#include <opencv2\opencv.hpp>

int main()
{
    // Load image
    cv::Mat1b img = cv::imread("path_to_img", cv::IMREAD_GRAYSCALE);

    // Correct image
    cv::Mat1b bin = img < 127;

    // Find contour
    std::vector<std::vector<cv::Point>> contours;
    cv::findContours(bin, contours, cv::RETR_EXTERNAL, cv::CHAIN_APPROX_SIMPLE);

    // Draw on mask
    cv::Mat1b mask(bin.rows, bin.cols, uchar(0));
    cv::drawContours(mask, contours, 0, cv::Scalar(255), cv::FILLED);

    // Distance Trasnsform
    cv::Mat1f dt;
    cv::distanceTransform(mask, dt, cv::DIST_L2, 5, cv::DIST_LABEL_PIXEL);

    // Find max value
    double max_val;
    cv::Point max_loc;
    cv::minMaxLoc(dt, nullptr, &max_val, nullptr, &max_loc);

    // Output image
    cv::Mat3b out;
    cv::cvtColor(img, out, cv::COLOR_GRAY2BGR);
    cv::circle(out, max_loc, max_val, cv::Scalar(0, 255, 0));

    return 0;
}

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