findChessboardCorners无法获得校准图像

Question

我正在尝试让OpenCV 2.4.5从我的网络摄像头识别棋盘图案。我无法做到这一点，所以我决定尝试使用“完美”的图像来实现它：

但它仍然无效 - patternFound每次都返回false。有谁知道我做错了什么？

#include <stdio.h>

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace cv;
using namespace std;

int main(){
    Size patternsize(8,8); //number of centers
    Mat frame = imread("perfect.png"); //source image
    vector<Point2f> centers; //this will be filled by the detected centers

    bool patternfound = findChessboardCorners(frame,patternsize,centers);

    cout<<patternfound<<endl;
    drawChessboardCorners(frame, patternsize, Mat(centers), patternfound);

    cvNamedWindow("window");
    while(1){
        imshow("window",frame);
        cvWaitKey(33);
    }
}

Answer 1

通过反复试验，我意识到patternize应该是7x7，因为它计算内部角落。这个参数必须准确 - 8x8不起作用，但也不会少于7x7。

Answer 2

而不是使用

Size patternsize(8,8); 

使用

Size patternsize(7,7);  

Answer 3

棋盘的宽度和高度不能是相同的长度，即它需要是不对称的。这可能是您问题的根源。 Here是一个关于使用OpenCV进行摄像机校准的非常好的教程。

下面是我用于校准的代码（测试并且功能齐全，但是我在我自己的某个处理线程中调用它，你应该在你的处理循环中调用它或者用来捕获你的帧）：

void MyCalibration::execute(IplImage* in, bool debug)
{
    const int CHESSBOARD_WIDTH = 8;
    const int CHESSBOARD_HEIGHT = 5;
    const int CHESSBOARD_INTERSECTION_COUNT = CHESSBOARD_WIDTH * CHESSBOARD_HEIGHT;

    //const bool DO_CALIBRATION = ((BoolProperty*)getProperty("DoCalibration"))->getValue();
    if(in->nChannels == 1)
        cvCopy(in,gray_image);
    else
        cvCvtColor(in,gray_image,CV_BGR2GRAY);

    int corner_count;
    CvPoint2D32f* corners = new CvPoint2D32f[CHESSBOARD_INTERSECTION_COUNT];
    int wasChessboardFound = cvFindChessboardCorners(gray_image, cvSize(CHESSBOARD_WIDTH, CHESSBOARD_HEIGHT), corners, &corner_count);

    if(wasChessboardFound) {
        // Refine the found corners
        cvFindCornerSubPix(gray_image, corners, corner_count, cvSize(5, 5), cvSize(-1, -1), cvTermCriteria(CV_TERMCRIT_ITER, 100, 0.1));

        // Add the corners to the array of calibration points
        calibrationPoints.push_back(corners);

        cvDrawChessboardCorners(in, cvSize(CHESSBOARD_WIDTH, CHESSBOARD_HEIGHT), corners, corner_count, wasChessboardFound);
    } 
}

万一你想知道班级成员，这是我的班级（IplImage在我编写的时候仍然存在）：

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv/cv.h>

class MyCalibration
{
private:
    std::vector<CvPoint2D32f*> calibrationPoints;

    IplImage *gray_image;

public:
    MyCalibration(IplImage* in);
    void execute(IplImage* in, bool debug=false);
    ~MyCalibration(void);
};

最后是构造函数：

MyCalibration::MyCalibration(IplImage* in)
{
    gray_image = cvCreateImage(cvSize(in->width,in->height),8,1);
}