Morphological closing is Morphological Dilation followed by Morphological Erosion with the same kernel width . It is transitively also a nonlinear Filter applied to a Signal.
- The net effect is that any spectral valley narrower than bins is filled; broader structures are preserved. The dual of Morphological Opening.
- This is a Stencil operation: each output depends only on a fixed neighborhood of surrounding inputs, with a dilation then erosion instead of a weighted sum. The order of operations matters.