鱼眼图像不失真的正确方法 [英] Correct way for fisheye images undistortion

问题描述

我已经完成了一些示例程序，该程序可以消除棋盘上的镜头变形，例如鱼眼图像，而且效果很好，这是屏幕截图

I've done some sample program that removes lens distortion from the chessboard like fish eye images, and it works ok, here's the screen shot

接下来，我想使用鱼眼棋盘图案(上面的右图)以消除相同的镜头失真，但从真实图像中消除了运气-曲率仍然保留在未失真的图像上， 因此我得到了这个

Next I wanted to use the fish eye chessboard pattern (right image above) in order to remove the same lens distortion but from the real image and had no luck - the curvature still remains on the undistorted image, thus I got this instead

代码

void getObjectPoints(cv::Size, std::vector<std::vector<cv::Point3f>>&);

bool getImagePoints(cv::Mat&, cv::Size&, std::vector<std::vector<cv::Point2f>>&);

void runCalibration(cv::Mat& image, cv::Matx33d&, cv::Vec4d&);

cv::Mat removeFisheyeLensDist(cv::Mat&, cv::Matx33d&, cv::Vec4d&);

// ... definitions    
void getObjectPoints(cv::Size patternSize, std::vector<std::vector<cv::Point3f>>& objectPoints)
{
    const float squareSize = 0.0015f;
    std::vector<cv::Point3f> knownBoardPositions;
    for (int i = 0; i < patternSize.height; ++i)
    {
        for (int j = 0; j < patternSize.width; ++j)
        {
            knownBoardPositions.push_back(cv::Point3f(j*squareSize, i*squareSize, 0.0f));
        }
    }
    if (knownBoardPositions.size() > 0)
        objectPoints.push_back(knownBoardPositions);
}

bool getImagePoints(cv::Mat& image, cv::Size& patternSize, std::vector<std::vector<cv::Point2f>>& imagePoints)
{
    bool patternFound = false;
    while (!patternFound)
    {
        std::vector<cv::Point2f> corners;
        for (int i = 7; i <= 30; ++i)
        {
            int w = i;
            int h = i - 2;

            patternFound = cv::findChessboardCorners(image, cv::Size(w, h), corners,
                                              cv::CALIB_CB_ADAPTIVE_THRESH | cv::CALIB_CB_NORMALIZE_IMAGE);
            if (patternFound)
            {
                patternSize.width = w;
                patternSize.height = h;
                imagePoints.push_back(corners);
                break;
            }
        }
    }

    return patternFound;
}

void runCalibration(cv::Mat& image, cv::Matx33d& K, cv::Vec4d& D)
{
    std::vector< std::vector<cv::Point2f> > imagePoints;
    std::vector< std::vector<cv::Point3f> > objectPoints;
    cv::Size patternSize;
    bool patternFound = getImagePoints(image, patternSize, imagePoints);

    if (patternFound)
    {
        getObjectPoints(patternSize, objectPoints);

        std::vector<cv::Vec3d> rvecs;
        std::vector<cv::Vec3d> tvecs;
        cv::fisheye::calibrate(
            objectPoints,
            imagePoints,
            image.size(),
            K,
            D,
            rvecs,
            tvecs,
            cv::fisheye::CALIB_FIX_SKEW |   cv::fisheye::CALIB_RECOMPUTE_EXTRINSIC
        |   cv::fisheye::CALIB_FIX_K1   |   cv::fisheye::CALIB_FIX_K2
        |   cv::fisheye::CALIB_FIX_K3   |   cv::fisheye::CALIB_FIX_K4
//            cv::TermCriteria(3, 20, 1e-6)
        );
    }
}

cv::Mat removeFisheyeLensDist(cv::Mat& distorted, cv::Matx33d& K, cv::Vec4d& D)
{
    cv::Mat undistorted;
    cv::Matx33d newK = K;
    cv::fisheye::undistortImage(distorted, undistorted, K, D, newK);
    return undistorted;
}

int main(int argc, char* argv[])
{
    cv::Mat chessBoardPattern = //..
    cv::Mat distortedImage = //...
    cv::imshow("distorted", distortedImage);

    cv::Matx33d K;  cv::Vec4d D;
    runCalibration(chessBoardPattern, K, D);
    cv::Mat undistoredImage = removeFisheyeLensDist(distortedImage, K, D);    
    cv::imshow("undistored", undistoredImage);
    cv::waitKey(0);
    return 0;
}

由于我认为带有塔的图像的曲率非常像右侧的棋盘，因此对于塔图像应该使用相同的图案...

As I think the image with the tower has very simillar curvatures as a chessboard on the right so the same pattern should've work for tower image ...

我在那里做错了什么? 为什么它不能解决塔像的镜头畸变?

What Am I doing wrong there ? And Why it's not fixing lens distortion for the tower image ?

推荐答案

不幸的是，您的假设

如果图像具有相同的曲率，则相机参数应大致相同，这样我就可以用棋盘图案使鱼眼图像不失真

if images have same curvatures thus the camera parameters should be approximately same and so I can undistort fisheye emage with a chessboard pattern

是错误的.即使是相同型号的相机，其焦距，镜头几何形状和位置等也会有所不同，需要分别进行校准.除了在使用相机的过程中，这些参数还会由于发热，振动和其他影响而改变(通常在实践中会被忽略).

is wrong. Even cameras of same model will have differences in focal distance, lens geometry and placement, etc, which need to be calibrated individually. Besides during usage of camera these parameters may change due to heating, vibration and other effects (usually this is ignored in practice).

要在不使用照相机的情况下使图像不失真，只需选择一些简单的鱼眼镜头照相机模型，然后尝试手动估算参数，尝试使直线看起来笔直(例如，使用带有所有参数的滑块的GUI).这可能很乏味，但是我不知道更好的选择.此外，某些图像编辑软件可能具有用于此目的的工具(如果我没记错的话，GIMP确实如此)

To undistort your image without having access to camera all you can do is just select some simple fisheye camera model and try to estimate parameters manually, trying to make straight lines look straight (for example using GUI with sliders for all parameters). This can be tedious, but I am not aware of better options. Besides, some image editing software may have tools for that (if I recall correctly GIMP does)

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