Opencv图像拼接或全景 [英] Opencv Image Stitching or Panorama

问题描述

我正在OpenCV(全景图)中进行图像拼接，但是我有一个问题.

I am doing image stitching in OpenCV (A panorama) but I have one problem.

我不能使用OpenCV中的Stitching类，因此必须仅使用特征点和单应性来创建它.

I can't use the class Stitching from OpenCV so I must create it with only feature points and homographies.

OrbFeatureDetector detector( minHessian );

std::vector<KeyPoint> keypoints_1, keypoints_2;

Mat descriptors_1a, descriptors_2a;
detector.detect( img_1, keypoints_1 , descriptors_1a);
detector.detect( img_2, keypoints_2 , descriptors_2a);

//-- Step 2: Calculate descriptors (feature vectors)
OrbDescriptorExtractor extractor;

Mat descriptors_1, descriptors_2;
cout<<"La distancia es " <<endl;
extractor.compute( img_1, keypoints_1, descriptors_1 );
extractor.compute( img_2, keypoints_2, descriptors_2 );

//-- Step 3: Matching descriptor vectors with a brute force matcher
BFMatcher matcher(NORM_HAMMING, true);
std::vector< DMatch > matches;
matcher.match( descriptors_1, descriptors_2, matches );

在这里我获得了比赛中的特征点，但是我需要对其进行过滤:

Here I obtain the feature points in matches, but I need to filter it:

 double max_dist = 0; double min_dist = 100;

  //-- Quick calculation of max and min distances between keypoints
  for( int i = 0; i < matches.size(); i++ )
  {
      double dist = matches[i].distance;

  //cout<<"La distancia es " << i<<endl;
    if( dist < min_dist && dist >3)
        {

            min_dist = dist;
        }
    if( dist > max_dist) max_dist = dist;
  }

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

  for( int i = 0; i < matches.size(); i++ )
  {
      //cout<<matches[i].distance<<endl;
      if( matches[i].distance < 3*min_dist && matches[i].distance > 3)
     {
          good_matches.push_back( matches[i]); }
  }

现在，我计算同形学

vector<Point2f> p1, p2;
    for (unsigned int i = 0; i < matches.size(); i++) {
        p1.push_back(keypoints_1[matches[i].queryIdx].pt);
        p2.push_back(keypoints_2[matches[i].trainIdx].pt);
    }

    // Homografía
    vector<unsigned char> match_mask;
    Mat h = findHomography(Mat(p1),Mat(p2), match_mask,CV_RANSAC);

最后，获得变换矩阵并应用warpPerspective获得两个图像的连接，但是我的问题是在最终图像中，照片周围出现黑色区域​​，当我再次循环时，最终图像将是易读的.

ANd finally, obtain the transform matrix and apply warpPerspective to obtain the join of the two images, but my problem is that in the final image, appears black areas around the photo, and when I loop again, the final image will be ilegible.

// Transformar perspectiva para imagen 2
    vector<Point2f> cuatroPuntos;
    cuatroPuntos.push_back(Point2f (0,0));
    cuatroPuntos.push_back(Point2f (img_1.size().width,0));
    cuatroPuntos.push_back(Point2f (0, img_1.size().height));
    cuatroPuntos.push_back(Point2f (img_1.size().width, img_1.size().height));
    Mat MDestino;
    perspectiveTransform(Mat(cuatroPuntos), MDestino, h);

    // Calcular esquinas de imagen 2
    double min_x, min_y, tam_x, tam_y;
    float min_x1, min_x2, min_y1, min_y2, max_x1, max_x2, max_y1, max_y2;
    min_x1 = min(MDestino.at<Point2f>(0).x, MDestino.at<Point2f>(1).x);
    min_x2 = min(MDestino.at<Point2f>(2).x, MDestino.at<Point2f>(3).x);
    min_y1 = min(MDestino.at<Point2f>(0).y, MDestino.at<Point2f>(1).y);
    min_y2 = min(MDestino.at<Point2f>(2).y, MDestino.at<Point2f>(3).y);
    max_x1 = max(MDestino.at<Point2f>(0).x, MDestino.at<Point2f>(1).x);
    max_x2 = max(MDestino.at<Point2f>(2).x, MDestino.at<Point2f>(3).x);
    max_y1 = max(MDestino.at<Point2f>(0).y, MDestino.at<Point2f>(1).y);
    max_y2 = max(MDestino.at<Point2f>(2).y, MDestino.at<Point2f>(3).y);
    min_x = min(min_x1, min_x2);
    min_y = min(min_y1, min_y2);
    tam_x = max(max_x1, max_x2);
    tam_y = max(max_y1, max_y2);

    // Matriz de transformación
    Mat Htr = Mat::eye(3,3,CV_64F);
    if (min_x < 0){
        tam_x = img_2.size().width - min_x;
        Htr.at<double>(0,2)= -min_x;
    }
    if (min_y < 0){
        tam_y = img_2.size().height - min_y;
        Htr.at<double>(1,2)= -min_y;
    }

    // Construir panorama
    Mat Panorama;
    Panorama = Mat(Size(tam_x,tam_y), CV_32F);
    warpPerspective(img_2, Panorama,     Htr, Panorama.size(), INTER_LINEAR, BORDER_CONSTANT,   0);
    warpPerspective(img_1, Panorama, (Htr*h), Panorama.size(), INTER_LINEAR, BORDER_TRANSPARENT,0);

任何人都知道如何消除这种黑色区域?我做不好吗?任何人都知道我可以看到的功能代码吗?

Anyone knows how can I eliminate this black areas? Is something that I do bad? Anyone knows a functional code that I can see to compare it?

感谢您的时间

那是我的形象

我想消除黑色部分.

推荐答案

正如Micka所建议的，在进行拼接时，全景图通常是波浪形的，因为单应性或其他投影方法不会将一个矩形映射到另一个矩形.您可以使用一些拉直"来补偿这种影响，请参考本文:

As Micka suggested, when you do stitching, the panorama is usually wavy, because homography or other projection methods do not map a rectangle to another rectangle. You can compensate this effect by using some "straightening", referring to this article:

M.布朗和D. G. Lowe.使用不变功能自动全景图像拼接. IJCV，74(1):59-73，2007

M. Brown and D. G. Lowe. Automatic panoramic image stitching using invariant features. IJCV, 74(1):59–73, 2007

关于裁剪黑色部分，我编写了可以使用的此类.此类假定图像为BGR，黑色像素的值为Vec3b(0,0,0).可以在这里访问源代码:

As to cropping the black part, I wrote this class that you can use. This class assumes the image is BGR and the black pixels have value Vec3b(0,0,0). The source code can be accessed here:

https://github.com/chmos/crop-images.git

最好

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