特征描述

目标

在本教程中，我们将涉及:

• 使用 DescriptorExtractor 接口来寻找关键点对应的特征向量. 特别地:
  • 使用 SurfDescriptorExtractor 以及它的函数 compute 来完成特定的计算.
  • 使用 BruteForceMatcher 来匹配特征向量。
  • 使用函数 drawMatches 来绘制检测到的匹配点.

理论

代码

这个教程代码如下所示. 你还可以 从这里下载到源代码

#include <stdio.h>
#include <iostream>
#include "opencv2/core/core.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/highgui/highgui.hpp"

using namespace cv;

void readme();

/** @function main */
int main( int argc, char** argv )
{
  if( argc != 3 )
   { return -1; }

  Mat img_1 = imread( argv[1], CV_LOAD_IMAGE_GRAYSCALE );
  Mat img_2 = imread( argv[2], CV_LOAD_IMAGE_GRAYSCALE );

  if( !img_1.data || !img_2.data )
   { return -1; }

  //-- Step 1: Detect the keypoints using SURF Detector
  int minHessian = 400;

  SurfFeatureDetector detector( minHessian );

  std::vector<KeyPoint> keypoints_1, keypoints_2;

  detector.detect( img_1, keypoints_1 );
  detector.detect( img_2, keypoints_2 );

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

  Mat descriptors_1, descriptors_2;

  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
  BruteForceMatcher< L2<float> > matcher;
  std::vector< DMatch > matches;
  matcher.match( descriptors_1, descriptors_2, matches );

  //-- Draw matches
  Mat img_matches;
  drawMatches( img_1, keypoints_1, img_2, keypoints_2, matches, img_matches );

  //-- Show detected matches
  imshow("Matches", img_matches );

  waitKey(0);

  return 0;
  }

 /** @function readme */
 void readme()
 { std::cout << " Usage: ./SURF_descriptor <img1> <img2>" << std::endl; }

解释

结果

1. 这是使用BruteForce 匹配两张图的结果: