Computes the spectral gradient over all bands of an image (or the first band if the image is Array typed) by computing the per-pixel difference between the spectral erosion and dilation with a given structuring kernel and distance metric. See: Plaza, Antonio, et al. 'Spatial/spectral endmember extraction by multidimensional morphological operations.' IEEE transactions on geoscience and remote sensing 40.9 (2002): 2025-2041.
| Usage | Returns | Image.spectralGradient(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. |