OpenCV C++ 畸变矫正、透视变换加速 _生活百科

前两周，同事和我说检测时间超时，其中对图像做畸变矫正和投影变换就要花费25ms（3000×3000的图）。而此时我们已经用上了文章opencv图像畸变矫正加速、透视变换加速方法总结中的方法。突然我想到了我去年笔记OpenCV笔记（10）相机模型与标定中的一个函数cv::undistortPoints()，对感兴趣点进行畸变矫正。在应用之前，需要测试下两种方法计算出来的点的差值，即remap和undistortPoints的不同。结论：对全图进行畸变矫正，再找点 VS 找点后，对点进行畸变矫正，两者的差值小于0.1个像素，可行！同样的方法可以运用在投影变换上。在尺寸测量方面，这样可以节省掉畸变矫正和投影变换的时间。
1 只对感兴趣的点进行畸变矫正// 读取相机参数文件FileStorage fs("D:/distortionLens.xml", FileStorage::READ);Mat intrinsic_matrix = Mat(3, 3, CV_32FC1, Scalar::all(0));Mat distortion_coeffs = Mat(1, 5, CV_32FC1, Scalar::all(0));fs["intrinsic_matrix"] >> intrinsic_matrix;fs["distortion_coeffs"] >> distortion_coeffs;Mat mapx = Mat(s, CV_32FC1);Mat mapy = Mat(s, CV_32FC1);// 根据内参和畸变系数，建立查找表//intrinsic_matrix = getOptimalNewCameraMatrix(intrinsic_matrix, distortion_coeffs, s, 1, s, 0);initUndistortRectifyMap(intrinsic_matrix, distortion_coeffs, Mat(),intrinsic_matrix, s, CV_32FC1, mapx, mapy);// 方法1：畸变矫正后找角点Mat distortionMat;remap(src, distortionMat, mapx, mapy, INTER_CUBIC);vector<Point2f> distortPoints;findChessboardCornersSB(src, Size(21, 21), distortPoints, 64);// 方法2：找角点后畸变矫正vector<Point2f> oriPoints, sparsePoints;findChessboardCornersSB(src, Size(21, 21), oriPoints, 64);undistortPoints(oriPoints, sparsePoints, intrinsic_matrix, distortion_coeffs, Mat(), intrinsic_matrix);// 打印比较cout << "原图找角点" << "\t" << "原图remap后找角点" << "\t" << "对原图角点矫正" << endl;for (int i = 0; i < sparsePoints.size(); i++) {cout << oriPoints[i] << "\t" << distortPoints[i] << "\t" << sparsePoints[i] << "\t" << "差值：" << distortPoints[i] - sparsePoints[i] << endl;}【OpenCV C++ 畸变矫正、透视变换加速】部分数据如下所示，可以看出，两者差值小于0.1个像素，加速10ms完成，接下来再对投影变换加速一下。

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2 只对感兴趣的点进行投影变换// 读取变换矩阵fs = FileStorage("D:/transMat.txt", FileStorage::READ);Mat transMat = Mat(3, 3, CV_32FC1, Scalar::all(0));fs["transMat"] >> transMat;// 方法1：进行透视变换后找角点Mat warpMat;warpPerspective(src, warpMat, transMat, s, INTER_LINEAR, BORDER_CONSTANT, Scalar(255));vector<Point2f> warpPoints;findChessboardCornersSB(warpMat,Size(21, 21), warpPoints, 64);// 方法2：找角点后进行透视变换vector<Point2f> outPoints;for (int i = 0; i < oriPoints.size(); i++) { Mat_<double> oriPoint(3, 1); oriPoint(0, 0) = oriPoints[i].x; oriPoint(1, 0) = oriPoints[i].y; oriPoint(2, 0) = 1; Mat dstPoints = transMat * oriPoint; double a1 = dstPoints.at<double>(0, 0); double a2 = dstPoints.at<double>(1, 0); double a3 = dstPoints.at<double>(2, 0); outPoints.push_back(Point2f(a1 * 1.0 / a3, a2 * 1.0 / a3));}//打印cout << "原图找角点" << "\t" << "原图透视变换后找角点" << "\t" << "对原图角点变换" << endl;for (int i = 0; i < sparsePoints.size(); i++) { cout << oriPoints[i] << "\t" << warpPoints[i] << "\t" << outPoints[i] << "\t" << "差值：" << distortPoints[i] - sparsePoints[i] << endl;}

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3 合并3.1 读取文件void GetMap(){ FileStorage fs(path+"distortionLens.xml", FileStorage::READ); if (fs.isOpened()) {intrinsic_matrix = Mat(3, 3, CV_64FC1, Scalar::all(0));distortion_coeffs = Mat(1, 5, CV_64FC1, Scalar::all(0));fs["intrinsic_matrix"] >> intrinsic_matrix;fs["distortion_coeffs"] >> distortion_coeffs; } fs = FileStorage(path+"transMat.txt", FileStorage::READ); if (fs.isOpened()) {transMat = Mat(3, 3, CV_64FC1, Scalar::all(0));fs["transMat"] >> transMat; }}3.2 变换感兴趣点void remapPoints(vector<Point2f>& points) { for (int i = 0; i < points.size(); i++) {Mat_<double> oriPoint(3, 1);oriPoint(0, 0) = points[i].x;oriPoint(1, 0) = points[i].y;oriPoint(2, 0) = 1;Mat dstPoint = transMat * oriPoint;double a1 = dstPoint.at<double>(0, 0);double a2 = dstPoint.at<double>(1, 0);double a3 = dstPoint.at<double>(2, 0);points[i] = Point2f(a1 * 1.0 / a3, a2 * 1.0 / a3); } undistortPoints(points, points, intrinsic_matrix, distortion_coeffs, Mat(), intrinsic_matrix);}