轮廓周围绘制矩形框和圆形框

实现顺序

彩色图转灰度图

滤波处理（高斯滤波/均值滤波）

二值化处理

发现轮廓，找到图形轮廓

通过api在轮廓点上找到最小包含矩形和圆，旋转矩形与椭圆

进行绘制

RDP算法API

approxPolyDP

InputArray curve 输入点集

OutputArray approxCurve 输出点集

double epsilon 点之间的步长

bool closed 形成的多边形是不是闭合曲线

轮廓周围绘制矩形

cv::boundingRect(InputArray points) 绘制最小矩形

cv::minAreaRect(InputArray points) 得到旋转矩形

cv::minEnclosingCircle() 得到最小圆形区域

InputArray points 最小圆点集

Point2f& center 圆心位置

float& radius 圆的半径

cv::fitEllipse()

InputArray points得到最小椭圆

#include"pch.h"
#include<iostream>
#include<math.h>
#include<opencv2/opencv.hpp>

using namespace std;
using namespace cv;

Mat gray_pic;
Mat src, dst;
int threshold_value = 170;
int threshold_max = 255;
void Contours(int, void*);
int main(int argc, char**argv)
{
    src = imread("2.jpg");
    namedWindow("output window", CV_WINDOW_AUTOSIZE);
    imshow("input window", src);
    cvtColor(src, gray_pic, COLOR_BGR2GRAY);
    blur(gray_pic, gray_pic, Size(3, 3), Point(-1, -1));
    createTrackbar("Threshold value", "output window", &threshold_value, threshold_max, Contours);
    Contours(0, 0);
    waitKey(0);
    return 0;
}

void Contours(int, void*)
{
    Mat binary_output;
    vector<vector<Point>> points;
    vector<Vec4i>hierachy;
    threshold(gray_pic, binary_output, threshold_value, threshold_max, THRESH_BINARY);
    
    findContours(binary_output, points, hierachy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(-1,-1));
    imshow("binray", binary_output);

    vector<vector<Point>> contours_ploy(points.size());
    vector<Rect> ploy_Rect(points.size());//矩形
    vector<Point2f>ccs(points.size());//圆心
    vector<float>radius(points.size());//半径

    vector<RotatedRect> minRects(points.size());//旋转矩形
    vector<RotatedRect> myellipse(points.size());//旋转椭圆
    for (size_t i = 0; i < contours_ploy.size(); ++i)
    {
        approxPolyDP(Mat(points[i]), contours_ploy[i], 3, true);
        ploy_Rect[i] = boundingRect(contours_ploy[i]);
        minEnclosingCircle(contours_ploy[i], ccs[i], radius[i]);
        if (contours_ploy[i].size() > 5)
        {
            myellipse[i] = fitEllipse(contours_ploy[i]);
            minRects[i] = minAreaRect(contours_ploy[i]);
        }
    }
    src.copyTo(dst);
    Point2f pts[4];
    //================================================================
    //矩形
    /*
    for (size_t t = 0; t < points.size(); ++t)
    {
        rectangle(src, ploy_Rect[t], Scalar(0, 0, 255),2, 8);
        //circle(src, ccs[t], radius[t], Scalar(0, 255, 0), 2, 8);
    }

    //imshow("output img", dst);
    imshow("output window", dst);
    */
    //====================================================================
    //圆形
    /*
    for (size_t t = 0; t < points.size(); ++t)
    {
        //rectangle(src, ploy_Rect[t], Scalar(0, 0, 255), 2, 8);
        circle(src, ccs[t], radius[t], Scalar(0, 255, 0), 2, 8);
    }

    //imshow("output img", dst);
    imshow("output window", dst);
    
    */
    //=========================================
    //使用API绘制
    
    for (size_t t = 0; t < points.size(); ++t)
    {
        if (contours_ploy[t].size() > 5)
        {
            ellipse(src, myellipse[t], Scalar(0, 0, 255), 1, 8);
            minRects[t].points(pts);
            for (int r = 0; r < 4; ++r)
            {
                line(src, pts[r], pts[(r + 1) % 4], Scalar(0, 255, 0), 1, 8);
            }
        }
    }

    //imshow("output img", dst);
    imshow("output window", dst);
    
}

注意vector不给size会报错