Drawing epipolar lines in OpenCV is not hard but it requires a sufficient amount of code. Here is a out-of-the-box function for your convenience which only needs the fundamental matrix and the matching points. And it even has an option to exclude outliers during drawing!
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | #include <opencv2/core/core.hpp>#include <opencv2/highgui/highgui.hpp>#include <opencv2/calib3d/calib3d.hpp>#include <opencv2/imgproc/imgproc.hpp>/** * \brief Compute and draw the epipolar lines in two images * associated to each other by a fundamental matrix * * \param title Title of the window to display * \param F Fundamental matrix * \param img1 First image * \param img2 Second image * \param points1 Set of points in the first image * \param points2 Set of points in the second image matching to the first set * \param inlierDistance Points with a high distance to the epipolar lines are * not displayed. If it is negative, all points are displayed **/template <typename T1, typename T2>static void drawEpipolarLines(const std::string& title, const cv::Matx<T1,3,3> F, const cv::Mat& img1, const cv::Mat& img2, const std::vector<cv::Point_<T2>> points1, const std::vector<cv::Point_<T2>> points2, const float inlierDistance = -1){ CV_Assert(img1.size() == img2.size() && img1.type() == img2.type()); cv::Mat outImg(img1.rows, img1.cols*2, CV_8UC3); cv::Rect rect1(0,0, img1.cols, img1.rows); cv::Rect rect2(img1.cols, 0, img1.cols, img1.rows); /* * Allow color drawing */ if (img1.type() == CV_8U) { cv::cvtColor(img1, outImg(rect1), CV_GRAY2BGR); cv::cvtColor(img2, outImg(rect2), CV_GRAY2BGR); } else { img1.copyTo(outImg(rect1)); img2.copyTo(outImg(rect2)); } std::vector<cv::Vec<T2,3>> epilines1, epilines2; cv::computeCorrespondEpilines(points1, 1, F, epilines1); //Index starts with 1 cv::computeCorrespondEpilines(points2, 2, F, epilines2); CV_Assert(points1.size() == points2.size() && points2.size() == epilines1.size() && epilines1.size() == epilines2.size()); cv::RNG rng(0); for(size_t i=0; i<points1.size(); i++) { if(inlierDistance > 0) { if(distancePointLine(points1[i], epilines2[i]) > inlierDistance || distancePointLine(points2[i], epilines1[i]) > inlierDistance) { //The point match is no inlier continue; } } /* * Epipolar lines of the 1st point set are drawn in the 2nd image and vice-versa */ cv::Scalar color(rng(256),rng(256),rng(256)); cv::line(outImg(rect2), cv::Point(0,-epilines1[i][2]/epilines1[i][1]), cv::Point(img1.cols,-(epilines1[i][2]+epilines1[i][0]*img1.cols)/epilines1[i][1]), color); cv::circle(outImg(rect1), points1[i], 3, color, -1, CV_AA); cv::line(outImg(rect1), cv::Point(0,-epilines2[i][2]/epilines2[i][1]), cv::Point(img2.cols,-(epilines2[i][2]+epilines2[i][0]*img2.cols)/epilines2[i][1]), color); cv::circle(outImg(rect2), points2[i], 3, color, -1, CV_AA); } cv::imshow(title, outImg); cv::waitKey(1);}template <typename T>static float distancePointLine(const cv::Point_<T> point, const cv::Vec<T,3>& line){ //Line is given as a*x + b*y + c = 0 return std::fabsf(line(0)*point.x + line(1)*point.y + line(2)) / std::sqrt(line(0)*line(0)+line(1)*line(1));} |
Thanks!
Hello, May I ask why the second point doing like this.
I give this two points (0, -c/b) and (-c/a, 0) to draw the line. Assume the line equation is ax+by+c = 0.
But it’s wrong.
cv::Point(img2.cols,-(epilines2[i][2]+epilines2[i][0]*img2.cols)/epilines2[i][1])