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Animating homography

Apr 26, 2021 opencv homography perspective-transform

A trick to animate the perspective transformation between two planes. The homography matrix is a 3x3 matrix computed from point correspondence.

This is explained in the previous post on homography

Here the homoraphy matrix is smoothly interpolated between the source image plane homography itself and the requited destination image plane. Used the addWeighted() function for this.

Code:

 vector<Point2f> pts_src;
  pts_src.push_back(Point2f(275, 194));
  pts_src.push_back(Point2f(211, 455));
  pts_src.push_back(Point2f(540, 479));  
  pts_src.push_back(Point2f(555, 212));

  vector<Point2f> pts_dst;
  pts_dst.push_back(Point2f(226, 314));
  pts_dst.push_back(Point2f(435, 511));
  pts_dst.push_back(Point2f(688, 374));  
  pts_dst.push_back(Point2f(463, 213));
   
  Mat s = findHomography(pts_src, pts_src);
  Mat d = findHomography(pts_src, pts_dst);
  
  for(int i=0; i<150; i++)
  {
      addWeighted (s,1-(i/150.0),d,(i/150.0),0,h);
      warpPerspective(im_src, im_out, h, im_dst.size());
      video.write (im_out);
  }

.