RANSAC using SIFT in Computer Vision

Question

Currently, I am doing a computer vision project. I used SIFT Matlab program using this: http://www.vlfeat.org/overview/sift.html codes. However, it gives me two matrices, one is matches and another is distances. I don't know how to convert these information to pixel values because in the next step I have to use RANSAC for getting the best matches. Would somebody please help me?

Answer 1

You have "matches", i.e. tentative correspondences, which means "feature with index I1 possibly corresponds to feature with index I2". So go the the list of the detected SIFT features and take coordinates of the I1 feature in image 1 and I2 in image 2.

Answer 2

The Computer Vision System Toolbox for MATLAB has various feature detectors and extractors, a function called matchFeatures to match the descriptors, and a function estimateGeometricTransform that uses RANSAC to do exactly what you need.

Please check out the following examples: Find Image Rotation and Scale Using Automated Feature Matching and Detect Objects in a Cluttered Scene Using Point Feature Matching