OpenCV-绘制圆端矩形（药丸）

Posted 2021-09-11 翟天保Steven

功能函数

// 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

#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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