Understanding RANSAC for estimating the homography matrix between pairs of points (matches)

• we need at least 3 point pairs (matches) to calculate an affine transformation
• we need at least 4 point pairs (matches) to calculate a perspective transformation

we can use RANSAC to calculate the homography matrix between matches.

Testing

we used surf to detect matches, then we pass these matches to apply_ransac function.

• detecting matches by surf:

• getting the homography matrix from apply_ransac function and transform image 1.jpg to 2.jpg:

Prerequisites

pip install numpy

pip install opencv-python (v3.4)

pip install matplotlib