feature based image alignment

Author: spmallick

ImageAlignment-FeatureBased/align.cpp

@@ -0,0 +1,78 @@
+#include <opencv2/opencv.hpp>
+#include "opencv2/xfeatures2d.hpp"
+#include "opencv2/features2d.hpp"
+
+using namespace std;
+using namespace cv;
+using namespace cv::xfeatures2d;
+
+const int MAX_MATCHES = 500;
+const float GOOD_MATCH_PERCENT = 0.15f;
+
+
+void alignImages(Mat &im1, Mat &im2, Mat &im1Reg, Mat &h)
+
+{
+  
+  // Convert images to grayscale
+  Mat im1Gray, im2Gray;
+  cvtColor(im1, im1Gray, CV_BGR2GRAY);
+  cvtColor(im2, im2Gray, CV_BGR2GRAY);
+  
+  // Variables to store keypoints and descriptors
+  std::vector<KeyPoint> keypoints1, keypoints2;
+  Mat descriptors1, descriptors2;
+  
+  // Detect ORB features and compute descriptors.
+  Ptr<Feature2D> orb = ORB::create(MAX_MATCHES);
+  orb->detectAndCompute(im1Gray, Mat(), keypoints1, descriptors1);
+  orb->detectAndCompute(im2Gray, Mat(), keypoints2, descriptors2);
+  
+  // Match features.
+  std::vector<DMatch> matches;
+  Ptr<DescriptorMatcher> matcher = DescriptorMatcher::create("BruteForce-Hamming");
+  matcher->match(descriptors1, descriptors2, matches, Mat());
+  
+  // Sort matches by score
+  std::sort(matches.begin(), matches.end());
+  
+  // Remove not so good matches
+  const int numGoodMatches = matches.size() * GOOD_MATCH_PERCENT;
+  matches.erase(matches.begin()+numGoodMatches, matches.end());
+  
+  
+  // Draw top matches
+  Mat imMatches;
+  drawMatches(im1, keypoints1, im2, keypoints2, matches, imMatches);
+  imwrite("matches.jpg", imMatches);
+  
+  
+  // Extract location of good matches
+  std::vector<Point2f> points1;
+  std::vector<Point2f> points2;
+  
+  for( size_t i = 0; i < matches.size(); i++ )
+  {
+    points1.push_back( keypoints1[ matches[i].queryIdx ].pt );
+    points2.push_back( keypoints2[ matches[i].trainIdx ].pt );
+  }
+  
+  // Find homography
+  h = findHomography( points1, points2, RANSAC );
+  
+  // Use homography
+  warpPerspective(im1, im1Reg, h, im2.size());
+  
+}
+
+
+int main(int argc, char **argv)
+{
+  Mat imReference = imread("form.jpg");
+  Mat im = imread("scanned-form.jpg");
+  Mat imReg, h;
+  
+  alignImages(im, imReference, imReg, h);
+  imwrite("aligned.jpg", imReg);
+  
+}