opencv4c++相机标定

相机标定是计算机视觉领域的重要基础工作之一，它可以帮助我们将相机的内外参数进行准确的测量和计算，从而提高图像处理和计算机视觉算法的精度。下面是使用OpenCV4C++实现相机标定的步骤：

1. 准备标定板
标定板需要满足一定的条件，如平整、边缘清晰、黑白相间等，以便于OpenCV能够准确地检测它。

2. 拍摄标定板图像
在不同的位置和角度拍摄标定板的多张图像，这些图像应该覆盖相机能够拍摄到的全部空间。

3. 检测标定板角点
使用OpenCV的函数cv::findChessboardCorners()检测标定板的角点，该函数返回一个bool值表示是否成功检测到角点，以及一个vector< Point2f >类型的变量存储检测到的角点坐标。

4. 标定相机
使用OpenCV的函数cv::calibrateCamera()进行相机标定，该函数需要输入多组不同位置下的标定板图像以及对应的角点坐标，输出相机的内外参数，如相机矩阵、畸变系数、旋转向量和平移向量等。

5. 评估标定结果
使用OpenCV的函数cv::calibrationMatrixValues()和cv::projectPoints()等函数评估标定结果的精度和准确度。

下面是一个简单的OpenCV4C++相机标定示例代码：

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main(int argc, char** argv)
{
    // 准备标定板
    Size boardSize(8, 6);  // 标定板内角点数
    float squareSize = 2.5f;  // 标定板方格尺寸
    vector<Point3f> objPoints;  // 实际空间角点
    for (int i = 0; i < boardSize.height; ++i) {
        for (int j = 0; j < boardSize.width; ++j) {
            objPoints.push_back(Point3f(j * squareSize, i * squareSize, 0));
        }
    }

    // 拍摄标定板图像
    vector<vector<Point2f>> imagePoints;  // 图像平面角点
    Mat frame, gray;
    VideoCapture cap(0);
    if (!cap.isOpened()) {
        cout << "Cannot open camera!" << endl;
        return -1;
    }
    while (imagePoints.size() < 10) {
        cap >> frame;
        cvtColor(frame, gray, COLOR_BGR2GRAY);
        vector<Point2f> corners;
        bool ret = findChessboardCorners(gray, boardSize, corners);
        if (ret) {
            cornerSubPix(gray, corners, Size(11, 11), Size(-1, -1), TermCriteria(TermCriteria::EPS + TermCriteria::MAX_ITER, 30, 0.1));
            imagePoints.push_back(corners);
            drawChessboardCorners(frame, boardSize, corners, ret);
        }
        imshow("Calibration", frame);
        waitKey(1);
    }

    // 标定相机
    Mat cameraMatrix, distCoeffs;
    vector<Mat> rvecs, tvecs;
    calibrateCamera(objPoints, imagePoints, frame.size(), cameraMatrix, distCoeffs, rvecs, tvecs);

    // 评估标定结果
    double fx = cameraMatrix.at<double>(0, 0);
    double fy = cameraMatrix.at<double>(1, 1);
    double cx = cameraMatrix.at<double>(0, 2);
    double cy = cameraMatrix.at<double>(1, 2);
    double k1 = distCoeffs.at<double>(0, 0);
    double k2 = distCoeffs.at<double>(0, 1);
    double p1 = distCoeffs.at<double>(0, 2);
    double p2 = distCoeffs.at<double>(0, 3);
    double k3 = distCoeffs.at<double>(0, 4);
    cout << "fx = " << fx << ", fy = " << fy << ", cx = " << cx << ", cy = " << cy << endl;
    cout << "k1 = " << k1 << ", k2 = " << k2 << ", p1 = " << p1 << ", p2 = " << p2 << ", k3 = " << k3 << endl;

    return 0;
}