一种基于圆形的特殊标记识别

由于项目需要，我之前做了一个基于圆形图案的标记识别，其目的是实现单目相机对标记物的识别和定位。标记如下所示：

这个东西有四个圆形组成，打印出来后，测量其尺寸，就可以通过识别其图像位置，再使用P4P解算，就可以得到该平面相对于相机的三维方向和倾角。

首先是识别：

		ima = ardrone.getImage();
	SimpleBlobDetector::Params params;
	params.minThreshold = 40;
	params.maxThreshold = 160;
	params.thresholdStep = 5;
	params.minArea = 100;
	params.minConvexity = 0.7f;
	params.minInertiaRatio = 0.8f;
	params.maxArea = 8000;

	params.filterByCircularity = true;
	params.minCircularity = 0.5;
	params.maxCircularity = 1.5;
	params.maxInertiaRatio = 1;
	params.maxConvexity = 1;

	cv::Ptr<cv::SimpleBlobDetector> detector = cv::SimpleBlobDetector::create(params);
	cvtColor(ima, gray, CV_BGR2GRAY); // smooth it, otherwise a lot of false circles may be detected 
		//normalize(gray, gray, 0, 255, 32);
		//cout << gray.rows <<' '<<gray.cols<< endl;
		std::vector<KeyPoint> keypoints;

if (keypoints.size() != pointnum)continue;

		int fail = 0;
		for (int i = 1; i < pointnum; i++)
		{
			if (abs(keypoints[0].size - keypoints[i].size) / keypoints[0].size > 0.3)fail = 1;
		}
		if (fail == 1)continue;
		vector<vector<int>>dis;
		for (int i = 0; i < pointnum; i++)
		{
			vector<int> temp;
			for (int j = 0; j < pointnum; j++)
			{