Fast quasi-flat zones filtering using area threshold and region merging

Quasi-flat zones are morphological operators which segment the image into homogeneous regions according to certain criteria. They are used as an image simplification tool or an image segmentation pre-processing, but they induced a very important oversegmentation. Several filtering methods have been proposed to deal with this issue but they suffer from different drawbacks, e.g., loss of quality or edge deformation. In this article, we propose a new method based on existing approaches which achieves better or similar results than existing approaches, does not suffer from their drawbacks and requires less computation time. It consists of two successive steps. First, small quasi-flat zones are removed according to a minimal area threshold. They are then filled through the growth of remaining zones.

► We review and compare existing quasi-flat zones filtering methods.
► We propose a new method which does not suffer from existing methods drawbacks.
► Our method removes small quasi-flat zones and then grows remaining zones.
► Our approach achieves better results in less computation time.