Affine Invariant Mathematical Morphology
   Applied to a Generic Shape Recognition Algorithm

We design a generic contrast and affine invariant planar shape recognition
algorithm. By generic, we mean an algorithm which delivers a list of all
shapes two digital images have in common, up to any affine transform or
contrast change. We define as "shape elements" all possible pieces of level
lines of the image. Their number can be drastically reduced by using affine
and contrast invariant smoothing Matheron operators, which we describe as
alternate affine erosions-dilations. We then discuss an efficient local
encoding of the shape elements. We finally show experiments. Applications
aimed at include image registration, image indexing, optical flow.