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2022
08-12

OpenCV绘制圆端矩形的示例代码

本文主要介绍了OpenCV绘制圆端矩形的示例代码，分享给大家，具体如下:

功能函数

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// 绘制圆端矩形（药丸状，pill）
void DrawPill(cv::Mat mask, const cv::RotatedRect &rotatedrect, const cv::Scalar &color, int thickness, int lineType)
{
    cv::Mat canvas = cv::Mat::zeros(mask.size(), CV_8UC1);
    // 确定短边，短边绘制圆形
    cv::RotatedRect rect = rotatedrect;
    float r = rect.size.height / 2.0f;
    if (rect.size.width > rect.size.height) {
        rect.size.width -= rect.size.height;
    }
    else {
        rect.size.height -= rect.size.width;
        r = rect.size.width / 2.0f;
    }
    cv::Point2f ps[4];
    rect.points(ps);
  
    // 绘制边缘
    std::vector<std::vector<cv::Point>> tmpContours;
    std::vector<cv::Point> contours;
    for (int i = 0; i != 4; ++i) {
        contours.emplace_back(cv::Point2i(ps[i]));
    }
    tmpContours.insert(tmpContours.end(), contours);
    drawContours(canvas, tmpContours, 0, cv::Scalar(255),5, lineType);  // 填充mask
  
    // 计算常长短轴
    float a = rotatedrect.size.width;
    float b = rotatedrect.size.height;
  
    int point01_x = (int)((ps[0].x + ps[1].x) / 2.0f);
    int point01_y = (int)((ps[0].y + ps[1].y) / 2.0f);
    int point03_x = (int)((ps[0].x + ps[3].x) / 2.0f);
    int point03_y = (int)((ps[0].y + ps[3].y) / 2.0f);
    int point12_x = (int)((ps[1].x + ps[2].x) / 2.0f);
    int point12_y = (int)((ps[1].y + ps[2].y) / 2.0f);
    int point23_x = (int)((ps[2].x + ps[3].x) / 2.0f);
    int point23_y = (int)((ps[2].y + ps[3].y) / 2.0f);
  
    cv::Point c0 = a < b ? cv::Point(point12_x, point12_y) : cv::Point(point23_x, point23_y);
    cv::Point c1 = a < b ? cv::Point(point03_x, point03_y) : cv::Point(point01_x, point01_y);
  
    // 长轴两端以填充的方式画圆，直径等于短轴
    cv::circle(canvas, c0, (int)r, cv::Scalar(255), 5, lineType);
    cv::circle(canvas, c1, (int)r, cv::Scalar(255), 5, lineType);
  
    // 绘制外围轮廓，如果不这样操作，会得到一个矩形加两个圆形，丑。。。
    std::vector<std::vector<cv::Point>> EXcontours;
    cv::findContours(canvas,EXcontours,cv::RETR_EXTERNAL, CHAIN_APPROX_SIMPLE);
    drawContours(mask, EXcontours, 0, color, thickness,lineType);  // 填充mask
}

测试代码

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#include <iostream>
#include <opencv2/opencv.hpp>
  
using namespace std;
using namespace cv;
  
void DrawPill(cv::Mat mask, const cv::RotatedRect &rotatedrect, const cv::Scalar &color, int thickness, int lineType);
  
int main()
{
    cv::Mat src = imread("test.jpg");
    cv::Mat result = src.clone();
    cv::RotatedRect rorect(cv::Point(src.cols / 2, src.rows / 2), cv::Size(1000, 800), 50);
    DrawPill(result, rorect, cv::Scalar(0, 255, 255),8,16);
    imshow("original", src);
    imshow("result", result);
    waitKey(0);
    return 0;
}
  
// 绘制圆端矩形（药丸状，pill）
void DrawPill(cv::Mat mask, const cv::RotatedRect &rotatedrect, const cv::Scalar &color, int thickness, int lineType)
{
    cv::Mat canvas = cv::Mat::zeros(mask.size(), CV_8UC1);
    // 确定短边，短边绘制圆形
    cv::RotatedRect rect = rotatedrect;
    float r = rect.size.height / 2.0f;
    if (rect.size.width > rect.size.height) {
        rect.size.width -= rect.size.height;
    }
    else {
        rect.size.height -= rect.size.width;
        r = rect.size.width / 2.0f;
    }
    cv::Point2f ps[4];
    rect.points(ps);
  
    // 绘制边缘
    std::vector<std::vector<cv::Point>> tmpContours;
    std::vector<cv::Point> contours;
    for (int i = 0; i != 4; ++i) {
        contours.emplace_back(cv::Point2i(ps[i]));
    }
    tmpContours.insert(tmpContours.end(), contours);
    drawContours(canvas, tmpContours, 0, cv::Scalar(255),5, lineType);  // 填充mask
  
    // 计算常长短轴
    float a = rotatedrect.size.width;
    float b = rotatedrect.size.height;
  
    int point01_x = (int)((ps[0].x + ps[1].x) / 2.0f);
    int point01_y = (int)((ps[0].y + ps[1].y) / 2.0f);
    int point03_x = (int)((ps[0].x + ps[3].x) / 2.0f);
    int point03_y = (int)((ps[0].y + ps[3].y) / 2.0f);
    int point12_x = (int)((ps[1].x + ps[2].x) / 2.0f);
    int point12_y = (int)((ps[1].y + ps[2].y) / 2.0f);
    int point23_x = (int)((ps[2].x + ps[3].x) / 2.0f);
    int point23_y = (int)((ps[2].y + ps[3].y) / 2.0f);
  
    cv::Point c0 = a < b ? cv::Point(point12_x, point12_y) : cv::Point(point23_x, point23_y);
    cv::Point c1 = a < b ? cv::Point(point03_x, point03_y) : cv::Point(point01_x, point01_y);
  
    // 长轴两端以填充的方式画圆，直径等于短轴
    cv::circle(canvas, c0, (int)r, cv::Scalar(255), 5, lineType);
    cv::circle(canvas, c1, (int)r, cv::Scalar(255), 5, lineType);
  
    // 绘制外围轮廓，如果不这样操作，会得到一个矩形加两个圆形，丑。。。
    std::vector<std::vector<cv::Point>> EXcontours;
    cv::findContours(canvas,EXcontours,cv::RETR_EXTERNAL, CHAIN_APPROX_SIMPLE);
    drawContours(mask, EXcontours, 0, color, thickness,lineType);  // 填充mask
}

测试效果

 

图1 原图

 

图2 绘制圆端矩形

绘制圆端矩形其实就是绘制了一个旋转矩形，然后分析哪个轴更长，就在哪个轴上的两端画圆，再取外围轮廓，大功告成，通俗来讲就画了一个矩形两个圆，如图3所示。

 

图3 绘制逻辑

不过注意，这个图形最好不要超过图像边界，因为超过后再分析外围轮廓，它认为的外围就到了内部，如图4所示。

 

图4 外围线

然后，你就会得到一个奇葩图形，如图5所示。

图5 示意图

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