Object recognition using affine and projective invariants of planar sets
Kalle Åström · 1993
A human with its highly complex and fine tuned visual system can easily recognize objects. It is however difficult to construct a computer program that can recognize general objects using visual input, e.g. from a CCD-camera. This paper treats recognition of planar non-algebraic curves. It is shown how invariant features, which are robust to occlusion, changes in lighting and viewpoint, can be extracted from a single gray-scale image. The invariant features can then be used in a fast recognition algorithm. Geometrical configurations are selected using edge detection and segmentation. Robust invariant features are then extracted from these configurations by choosing first a canonical or normal reference frame, and then features in this reference frame. These features automatically become invariant. In this work methods are given where a global and stable approach is used both in choosing the normal reference frame and in extracting invariants under affine and projective transformations. These...