Computes the spectral/spatial erosion of an image by computing the spectral distance of each pixel under a structuring kernel from the centroid of all pixels under the kernel and taking the closest result. See 'Spatial/spectral endmember extraction by multidimensional morphological operations.' IEEE transactions on geoscience and remote sensing 40.9 (2002): 2025-2041.

Usage	Returns
Image.spectralErosion(metric,kernel,useCentroid)	Image

Argument	Type	Details
this:image	Image	The input image.
metric	String, default: "sam"	The spectral distance metric to use. One of 'sam' (spectral angle mapper), 'sid' (spectral information divergence), 'sed' (squared Euclidean distance), or 'emd' (earth movers distance).
kernel	Kernel, default: null	Connectedness kernel. Defaults to a square of radius 1 (8-way connected).
useCentroid	Boolean, default: false	If true, distances are computed from the mean of all pixels under the kernel instead of the kernel's center pixel.