基于opencv的图像拼接（一）： sift特征点提取

网上有很多关于sift理论知识的介绍，在这里就不赘述了；

附上有关sift特征点提取的相关程序，需要注意的如下：

1. 使用opencv封装好的sift模块时， 需要加上

#include <opencv2/nonfree/nonfree.hpp>

2. SiftFeatureDetector 和 SiftDescriptorExtractor 意义不同，

SiftFeatureDetector 是为提取特征点位置和角度，一般保存到keypoint中，多用于在图中显现特征点；

SiftDescriptorExtractor是真正在后续实验中要用到的特征向量；

在程序中也会有专门讲解。

#include <iostream>#include <opencv2/highgui/highgui.hpp>#include <opencv2/nonfree/nonfree.hpp>  //sift算子需要用到的#include <opencv2/legacy/legacy.hpp>#include <vector>using namespace std;using namespace cv;Mat cacSIFTFeatureAndCompare(Mat srcImage1, Mat srcImage2 ){   //灰度及归一化Mat grayMat1, grayMat2;cvtColor(srcImage1, grayMat1, CV_BGR2GRAY);normalize(grayMat1, grayMat1, 0, 255, NORM_MINMAX);cvtColor(srcImage2, grayMat2, CV_BGR2GRAY);normalize(grayMat2, grayMat2, 0, 255, NORM_MINMAX);//定义sift描述子SiftFeatureDetector detector;SiftDescriptorExtractor extractor;//特征提取器//特征点检测vector<KeyPoint>keypoint1;vector<KeyPoint>keypoint2;detector.detect(grayMat1, keypoint1);//提取到特征点的位置和角度，保存在keypointdetector.detect(grayMat2, keypoint2);//计算特征点描述子Mat descriptions1, descriptions2;extractor.compute(grayMat1, keypoint1, descriptions1);extractor.compute(grayMat2, keypoint2, descriptions2);//做实验中要用到的Mat src_description1, src_description2;drawKeypoints(srcImage1,keypoint1,src_description1);drawKeypoints(srcImage2,keypoint2,src_description2);imshow("pic1_descriptions", src_description1);imshow("pic2_descriptions", src_description2);//特征点匹配  匹配用到的是比较简单的匹配vector<DMatch>matches;BruteForceMatcher<L2<float>>matcher;matcher.match(descriptions1,descriptions2,matches);//二分排序int N = 80;nth_element(matches.begin(), matches.begin()+N-1,matches.end());matches.erase(matches.begin()+N, matches.end());//绘制检测结果Mat matchMat;drawMatches(srcImage1,keypoint1,srcImage2,keypoint2,matches,matchMat);return matchMat;}int main(){Mat srcImage1 = imread("E:\\my\\pic_save\\angle_y1.jpg", 1);Mat srcImage2 = imread("E:\\my\\pic_save\\angle_x1.jpg", 1);Mat resSiftMatchMat = cacSIFTFeatureAndCompare(srcImage1,srcImage2);imshow("resSiftMatchMat", resSiftMatchMat);waitKey(0);return 0;}