OpenCV绘制圆角矩形的方法实例

功能函数

// 绘制圆角矩形
void DrawRotatedRectChamfer(cv::Mat mask,const cv::RotatedRect rotatedrect, float radius,const cv::Scalar &color, int thickness, int lineType)
{
	// 创建画布
	cv::Mat canvas = cv::Mat::zeros(mask.size(), CV_8UC1);

	cv::RotatedRect newrotatedrect = rotatedrect;

	//画宽缩减后的矩形
	cv::RotatedRect r1 = newrotatedrect;
	r1.size.width = r1.size.width - 2 * radius;
	DrawRotatedRect(canvas, r1, cv::Scalar(255), 5, lineType);

	//画高缩减后的矩形
	cv::RotatedRect r2 = newrotatedrect;
	r2.size.height = r2.size.height - 2 * radius;
	DrawRotatedRect(canvas, r2, cv::Scalar(255), 5,lineType);

	//画四个角的圆
	cv::RotatedRect r3 = r2;
	r3.size.width = r1.size.width;

	cv::Point2f ps[4];
	r3.points(ps);

	for (int i = 0; i != 4; ++i) {
		cv::circle(canvas, ps[i], (int)radius, cv::Scalar(255), 5);
	}
	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

}

// 绘制旋转矩形
void DrawRotatedRect(cv::Mat mask,const cv::RotatedRect rotatedrect,const cv::Scalar &color, int thickness,int lineType)
{
	cv::Point2f ps[4];
	rotatedrect.points(ps);

	std::vector<std::vector<cv::Point>> tmpContours;    // 创建一个InputArrayOfArrays 类型的点集
	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(mask, tmpContours, 0, color, thickness, lineType);  // 填充mask
}

测试代码

#include <iostream>
#include <opencv2/opencv.hpp>
#include <stdio.h>
using namespace std;
using namespace cv;

void DrawRotatedRectChamfer(cv::Mat mask, const cv::RotatedRect rotatedrect, float radius, const cv::Scalar &color, int thickness, int lineType);
void DrawRotatedRect(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(800, 600), 50);
	DrawRotatedRectChamfer(result, rorect, 100, cv::Scalar(0, 0, 255), 5, 16);
	imshow("original", src);
	imshow("result", result);
	waitKey(0);
	return 0;
}

// 绘制圆角矩形
void DrawRotatedRectChamfer(cv::Mat mask,const cv::RotatedRect rotatedrect, float radius,const cv::Scalar &color, int thickness, int lineType)
{
	// 创建画布
	cv::Mat canvas = cv::Mat::zeros(mask.size(), CV_8UC1);

	cv::RotatedRect newrotatedrect = rotatedrect;

	//画宽缩减后的矩形
	cv::RotatedRect r1 = newrotatedrect;
	r1.size.width = r1.size.width - 2 * radius;
	DrawRotatedRect(canvas, r1, cv::Scalar(255), 5, lineType);

	//画高缩减后的矩形
	cv::RotatedRect r2 = newrotatedrect;
	r2.size.height = r2.size.height - 2 * radius;
	DrawRotatedRect(canvas, r2, cv::Scalar(255), 5,lineType);

	//画四个角的圆
	cv::RotatedRect r3 = r2;
	r3.size.width = r1.size.width;

	cv::Point2f ps[4];
	r3.points(ps);

	for (int i = 0; i != 4; ++i) {
		cv::circle(canvas, ps[i], (int)radius, cv::Scalar(255), 5);
	}
	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

}

// 绘制旋转矩形
void DrawRotatedRect(cv::Mat mask,const cv::RotatedRect rotatedrect,const cv::Scalar &color, int thickness,int lineType)
{
	cv::Point2f ps[4];
	rotatedrect.points(ps);

	std::vector<std::vector<cv::Point>> tmpContours;    // 创建一个InputArrayOfArrays 类型的点集
	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(mask, tmpContours, 0, color, thickness, lineType);  // 填充mask
}

测试效果

图1 原图

图2 绘制圆角矩形

绘制圆角矩形其实是绘制了两个旋转矩形，交叉组合，然后以四交点为圆心绘制圆，就组成了圆角矩形，如图3所示。

图3 绘制逻辑

同理，这个最好不要绘制到图像外面，否则它在分析外围线的时候会出错，可以多加些判断来修正，我就不写了，交给兄弟们研究一下~

总结

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