使用OpenCV，C ++的桑普森距离

Question

I'm trying to calculate the Sampson distance , the distance from a point to it's corresponding epipolar line which I will use as an error metric later. I'm using opencv 3.1 , c++ , and windows-10 visual studio 14 .

But the function sampsonDistance crashes the code:

Point3f point1 = Point3f(keypoints_1[good_matches[iP].queryIdx].pt.x, keypoints_1[good_matches[iP].queryIdx].pt.y, 1.0);
Point3f point2 = Point3f(keypoints_2[good_matches[iP].trainIdx].pt.x, keypoints_2[good_matches[iP].trainIdx].pt.y, 1.0);            

Mat pt1(point1);
Mat pt2(point2);

double sampsonD = sampsonDistance(pt1, pt2, Flist[iF])

I get the error message:

OpenCV Error: Assertion failed (_pt1.type() == CV_64F && _pt1.type() == CV_64F && _F.type() == CV_64F) in cv::sampsonDistance, file D:\opencv\sources\modules\calib3d\src\fundam.cpp, line 1043

The documentation says:

double cv::sampsonDistance  ( InputArray  pt1,  
InputArray  pt2,  
InputArray  F  
) 

How do I use this function, I don't really understand the usage of the input array, in the above I convert a 3d point into what I believe is 2D homogeneous coordinates stored as a cv::Mat. The fundamental matrix is stored at a 3x3 cv::Mat.

Answer 1

From the error message, the points and the fundamental matrix have to be CV_64F (double type).

For the points, it should be:

Point3d point1 = Point3d(keypoints_1[good_matches[iP].queryIdx].pt.x, keypoints_1[good_matches[iP].queryIdx].pt.y, 1.0);
Point3d point2 = Point3d(keypoints_2[good_matches[iP].trainIdx].pt.x, keypoints_2[good_matches[iP].trainIdx].pt.y, 1.0);