Invariance
Suppose we are comparing two images I1 and I2
•I2 may be a transformed version of I1
•What
kinds of transformations are we likely to encounter in practice?
We’d like to find the same features regardless of the transformation
•This
is called transformational invariance
•Most
feature methods are designed to be invariant to
–Translation,
2D rotation, scale
•They
can usually also handle
–Limited
3D rotations (SIFT works up to about 60 degrees)
–Limited
affine transformations (some are fully affine invariant)