Real-time implementation of morphological filters with polygonal structuring elements

Abstract

In mathematical morphology, circular structuring elements (SE) are used whenever one needs angular isotropy. The circles--difficult to implement efficiently--are often approximated by convex, symmetric polygons that decompose under the Minkowski addition to 1-D inclined segments. In this paper, we show how to perform this decomposition efficiently, in stream with almost optimal latency to compute gray-scale erosion and dilation by flat regular polygons. We further increase its performance by introducing a spatial parallelism while maintaining sequential access to data. We implement these principles in a dedicated hardware block. Several of these blocks can be concatenated to efficiently compute sequential filters, or granulometries in one scan. With a configurable image size and programmable SE size, this architecture is usable in high-end, real-time industrial applications. We show on an example that it conforms to real-time requirements of the 100Hz 1080p FullHD TV standard, even for serial morphological filters using large hexagons or octagons.