11. Harris corner detector Equivalently, for small shifts [ u,v ] we have a bilinear approximation: , where M is a 2 ď´ 2 matrix computed from image derivatives :
12.
13. Harris corner detector Intensity change in shifting window: eigenvalue analysis ďŹ 1 , ďŹ 2 â eigenvalues of M direction of the slowest change direction of the fastest change ( ďŹ max ) -1/2 ( ďŹ min ) -1/2 Ellipse E(u,v) = const
14. Harris corner detector ďŹ 1 ďŹ 2 Corner ďŹ 1 and ďŹ 2 are large, ďŹ 1 ~ ďŹ 2 ; E increases in all directions ďŹ 1 and ďŹ 2 are small; E is almost constant in all directions edge ďŹ 1 >> ďŹ 2 edge ďŹ 2 >> ďŹ 1 flat Classification of image points using eigenvalues of M :
15. Harris corner detector Measure of corner response: ( k â empirical constant, k = 0.04-0.06)