opencv使用笔记——获取rotatedRect的内部区域mask

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一开始想的是传统的水漫法，但是想着矩形这么规则，应该可以有别的方法，于是想到了下面这种小trick。

1.首先计算rotatedRect的四个顶点。

RotatedRect rRect(Point2f(100, 100), Size2f(100, 50), 30);
	Point2f vertices[4];      //定义矩形的4个顶点
	rRect.points(vertices);   //计算矩形的4个顶点

2，然后根据旋转角度和中点位置计算旋转矩阵

cv::Mat rot_mat = cv::getRotationMatrix2D(Point2f(100, 100), 30, 1.0);

3.然后将顶点乘以旋转矩阵，进行旋转变换，用于生成一个规则的水平矩形Rect，然后就方便填充了

Mat background = Mat::zeros(back.size(), CV_8UC1);

for (int i = 0; i < 4; i++){
		Mat point_mat = (Mat_(3, 1) << vertices[i].x, vertices[i].y, 1.0);
		Mat point_rot = rot_mat * point_mat;
		Point2f p(point_rot.ptr(0)[0], point_rot.ptr(1)[0]);
		pp.push_back(p);
	}

	Rect rrr = boundingRect(pp);
	background(rrr) = 255;

       

4.最后再根据旋转矩阵，将矩形框仿射变换回去就行了。

rot_mat = cv::getRotationMatrix2D(Point2f(100, 100), -30, 1.0);
	cv::warpAffine(background, background, rot_mat, Size2f(200, 200));
	img.copyTo(back, background);

 

 

完整代码如下：

#include 
#include
#include

using namespace std;
using namespace cv;

int main()
{
	Mat img = Mat(200,200,CV_8UC3,Scalar(255,255,255));
	Mat back = Mat(200, 200, CV_8UC3, Scalar(0, 0, 0));
	Mat background = Mat::zeros(back.size(), CV_8UC1);
	RotatedRect rRect(Point2f(100, 100), Size2f(100, 50), 30);
	Point2f vertices[4];      //定义矩形的4个顶点
	Point2d vertices_d[4];
	rRect.points(vertices);   //计算矩形的4个顶点

	//Rect brect = rRect.boundingRect2f();
	//back(brect) = 255;
	//ellipse(back, rRect, cv::Scalar(0, 255, 255), 2, 8);


	for (int i = 0; i < 4; i++){
		line(back, vertices[i], vertices[(i + 1) % 4], Scalar(0, 255, 0));
	
	}

	cv::Mat rot_mat = cv::getRotationMatrix2D(Point2f(100, 100), 30, 1.0);
	cout << rot_mat< pp;

	//根据旋转矩阵进行仿射变换
	imshow("1", back);

	Mat dst;
	cv::warpAffine(back, dst, rot_mat, Size2f(200, 200));
	imshow("2",dst);
	for (int i = 0; i < 4; i++){
		Mat point_mat = (Mat_(3, 1) << vertices[i].x, vertices[i].y, 1.0);
		cout << point_mat <(0)[0], point_rot.ptr(1)[0]);
		circle(dst, p, 2, Scalar(0, 255, 0));
		pp.push_back(p);
	}

	Rect rrr = boundingRect(pp);
	background(rrr) = 255;
	imshow("3", background);

	rot_mat = cv::getRotationMatrix2D(Point2f(100, 100), -30, 1.0);
	Mat temp1;
	cv::warpAffine(background, background, rot_mat, Size2f(200, 200));
	img.copyTo(back, background);
	
	imshow("4", back);
	waitKey(0);
	return 0;
}

 

 

MMP,突然发现，opencv里面有现成的函数可以用！！！

drawContours!!

fine,此帖煞笔，此帖终结。。。。。

tips：该函数的输入数据为int型