Real-time implementation of morphological filters with polygonal structuring elements

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.