A Primer to Flooding, Razing and Watersheds

In the primer on morphology, this chapter focuses on catchment zones and lakes of a topographic relief. It explains perception of the topographic structures and shows in how many different ways they intervene in the field of image processing, for filtering or segmenting images. The regional minima of a flooded topographic surface are dry or are lakes. Flooding and razing have a very remarkable property: they create flat zones by filling valleys with lakes and by razing summits. The watershed partitions associated with increasing flooding form hierarchies. The chapter presents methods for reducing or suppressing the overlapping of catchment zones, producing the so‐called watershed partitions. It characterizes the topography of graphs as the topography of a relief, by observing the trajectory of a drop of water deposited on the relief. Node‐weighted graphs may represent many structures other than images, and the tools developed for analyzing images may be used in much different contexts.