Invariant to Rotation?
Invariance to image intensity?
Invariant to image scale?
Ellipse rotates but its shape(i.g. eigenvalues) remain the same
Corner response R is invariant to image rotation
Mostly invariant to additive and multiplicative intensity changes
only derivatives are used
intensity scale
Invariant to image scale
Not invariant to image scale
but can we do something about this
Consider regions(e.g. circles) of different size around a point
A region which is “scale invariant”
Not affected by the size but will be the same for “corresponding regions”
At a point, compute the scale invariant function over different size neighborhoods
Choose the scale for each image at which the function is a maximum
Sift scale invariant feature transform
specific suggestion use pyramid to find maximum values (remember edge detective) then eliminate “edges” and pick only corners
Harris-Laplacian
Find local maximum of
– harris corner
detector in space (image coordinates)
Laplacian in scale
