SIFT - local detector

• Filter size grows by N instead if $N^2$
• DoG - Difference of gaussian

extracting SIFT keypoints

1. Choose the maxima within 3x3x3 neighborhood.
   1. 26 neighbors (not including self)
      1. Sigma value tells you how big the blob is

• k is arbitrary scaler

• not perspective invariant

related resources

• http://www.aishack.in/2010/05/sift-scale-invariant-feature-transform/