File size: 3,355 Bytes
2b7d279 | 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 | #include "GlobalMotionCompensation.h"
GlobalMotionCompensation::~GlobalMotionCompensation() {}
/**
* @brief Applies global motion compensation to align the current frame with the previous frame.
*
* This function estimates the global motion between the current frame and the previous frame using keypoint detection and (Sparse) optical flow.
* It computes an affine transformation matrix to compensate for camera motion, returning a 2x3 matrix representing the transformation.
* The function handles initialization for the first frame, downscaling for execution time efficiency, and robust matching to ensure reliable motion estimation.
* The result is used to compensate predicted motion of an object.
*
* @param frame_raw The input frame (BGR color image) to be processed for motion compensation.
*
* @return A 2x3 Eigen::MatrixXf representing the affine transformation matrix to align the current frame with the previous frame.
* Returns an identity matrix if no motion estimation is possible (first frame or insufficient matches).
*/
Eigen::MatrixXf GlobalMotionCompensation::apply(const cv::Mat &frame_raw) {
// Initialization
int height = frame_raw.rows;
int width = frame_raw.cols;
Eigen::MatrixXf H = Eigen::MatrixXf::Zero(2, 3);
H.setIdentity();
cv::Mat frame;
cv::cvtColor(frame_raw, frame, cv::COLOR_BGR2GRAY);
// Downscale
if (_downscale > 1.0F) {
width /= _downscale, height /= _downscale;
cv::resize(frame, frame, cv::Size(width, height));
}
if (!_first_frame_initialized) {
/**
* If this is the first frame, there is nothing to match
* Save the keypoints and descriptors, return identity matrix
*/
_first_frame_initialized = true;
_prev_frame = frame.clone();
return H;
}
// Detect keypoints
std::vector <cv::Point2f> prev_pts;
cv::goodFeaturesToTrack(_prev_frame, prev_pts, 200, 0.01, 30, cv::noArray(), 3);
// Find correspondences between the previous and current frame
std::vector <cv::Point2f> matched_keypoints;
std::vector <uchar> status;
std::vector<float> err;
try {
cv::calcOpticalFlowPyrLK(_prev_frame, frame, prev_pts, matched_keypoints, status, err);
}
catch (const cv::Exception &e) {
std::cout << "Warning: Could not find correspondences for GMC" << std::endl;
_prev_frame = frame.clone();
return H;
}
// Keep good matches
std::vector <cv::Point2f> prev_points, curr_points;
for (size_t i = 0; i < matched_keypoints.size(); i++) {
if (status[i]) {
prev_points.push_back(prev_pts[i]);
curr_points.push_back(matched_keypoints[i]);
}
}
// Estimate affine matrix
if (prev_points.size() > 4) {
cv::Mat homography = cv::estimateAffine2D(prev_points, curr_points);
//cv::Mat inliers;
//cv::Mat homography = cv::findHomography(prev_points, curr_points, cv::RANSAC, 3,inliers, 500, 0.99);
H << homography.at<double>(0, 0), homography.at<double>(0, 1), homography.at<double>(0, 2),
homography.at<double>(1, 0), homography.at<double>(1, 1), homography.at<double>(1, 2);
}
_prev_frame = frame.clone();
return H;
} |