C++

Question

我正在尝试通过 OpenCV 使用 ORB 进行检测并使用 FLANN 进行匹配来提取和匹配特征，但我得到了一个非常奇怪的结果。加载我的 2 张图像并将它们转换为灰度后，这是我的代码：

// Initiate ORB detector
    Ptr<FeatureDetector> detector = ORB::create();

// find the keypoints and descriptors with ORB
    detector->detect(gray_image1, keypoints_object);
    detector->detect(gray_image2, keypoints_scene);

    Ptr<DescriptorExtractor> extractor = ORB::create();
    extractor->compute(gray_image1, keypoints_object, descriptors_object );
    extractor->compute(gray_image2, keypoints_scene, descriptors_scene );

// Flann needs the descriptors to be of type CV_32F
    descriptors_scene.convertTo(descriptors_scene, CV_32F);
    descriptors_object.convertTo(descriptors_object, CV_32F);

    FlannBasedMatcher matcher;
    vector<DMatch> matches;
    matcher.match( descriptors_object, descriptors_scene, matches );

    double max_dist = 0; double min_dist = 100;

    //-- Quick calculation of max and min distances between keypoints
    for( int i = 0; i < descriptors_object.rows; i++ )
    {
        double dist = matches[i].distance;
        if( dist < min_dist ) min_dist = dist;
        if( dist > max_dist ) max_dist = dist;
    }

    //-- Use only "good" matches (i.e. whose distance is less than 3*min_dist )
    vector< DMatch > good_matches;

    for( int i = 0; i < descriptors_object.rows; i++ )
    {
        if( matches[i].distance < 3*min_dist )
        {
            good_matches.push_back( matches[i]);
        }
    }


    vector< Point2f > obj;
    vector< Point2f > scene;


    for( int i = 0; i < good_matches.size(); i++ )
    {
        //-- Get the keypoints from the good matches
        obj.push_back( keypoints_object[ good_matches[i].queryIdx ].pt );
        scene.push_back( keypoints_scene[ good_matches[i].trainIdx ].pt );
    }

    // Find the Homography Matrix
    Mat H = findHomography( obj, scene, CV_RANSAC );
    // Use the Homography Matrix to warp the images
    cv::Mat result;
    warpPerspective(image1,result,H,Size(image1.cols+image2.cols,image1.rows));
    cv::Mat half(result,cv::Rect(0,0,image2.cols,image2.rows));
    image2.copyTo(half);
    imshow( "Result", result );

这是我得到的奇怪结果的屏幕截图： screen shot

可能是什么问题？

谢谢！

Answer 1

您遇到了错误匹配的结果：适合数据的单应性不是 "realistic"，因此扭曲了图像。

您可以像 example 中那样使用 imshow( "Good Matches", img_matches ); 调试匹配。

有多种方法可以改善您的比赛：

使用crossCheck选项
使用SIFT ratio test
使用 cv::findHompgraphy 中的 OutputArray mask 来识别完全错误的单应计算
...等等...

Answer 2

ORB 是二进制特征向量，不适用于 Flann。请改用蛮力 (BFMatcher)。

C++ - 使用 ORB 的 OpenCV 特征检测

C++ - OpenCV feature detection with ORB

opencv

orb

flann