Noise-resistant invariants of curves

Projective invariants are shape descriptors that are independent of the point of view from which the shape is seen, and, therefore, are of major importance in object recognition. They make it possible to match an image of an object to one stored in a database without the need for searching for the correct viewpoint. An invariant representation of a general curve is obtained. The calculation is local and does not suffer from the occlusion problem of global descriptors. To make the method robust, differentiation techniques that give much more reliable results than previous ones are developed. These differentiation methods are useful in many other applications as well