视觉SLAM十四讲遇到的问题

问题1 CH7：feature_extraction.cpp

代码：

    cout<<"c0:"<<keypoints_1[0].pt<<keypoints_2[0].pt<<endl;
    cout<<"c1:"<<keypoints_1[1].pt<<keypoints_2[1].pt<<endl;
    cout<<"c2:"<<keypoints_1[2].pt<<keypoints_2[2].pt<<endl;    
    cout<<"c3:"<<keypoints_1[3].pt<<keypoints_2[3].pt<<endl;    

输出结果：

c1:[138, 208][426, 160]
c2:[229, 174][377, 165]
c3:[229, 140][209, 160]

为什么特征点的坐标没有按照行或者列排序呢？

问题2 CH7：pose_estimation_3d2d.cpp

ushort d = d1.ptr<unsigned short> (int ( keypoints_1[m.queryIdx].pt.y )) [ int ( keypoints_1[m.queryIdx].pt.x ) ];

上面那段代码中为什么先y后x？