Uniformity-Based Superpixel Segmentation of Hyperspectral Images

Superpixel segmentation algorithms attempt to group contiguous image pixels which are in homogeneous regions into segments (superpixels). Superpixel segmentation maps have proven successful in improving the performance of unmixing algorithms on hyperspectral images. For hyperspectral images (HSIs), segment members must contain spectrally similar pixels, a requirement we refer to as segment uniformity. Existing superpixel segmentation algorithms which have been applied to HSIs provide no guarantees on the uniformity inside segments. In the absence of such guarantees, the only viable option is to make the segments small enough that uniformity is always ensured; this leads to an oversegmentation of the image. An accurate uniformity measure would lead to a more accurate segmentation. We propose a graph-based agglomerative approach that enforces segment uniformity by setting a threshold for maximum variability inside segments. The threshold is computed by a statistical analysis of the within-class and between-class spectral divergences of several mineral families of interest. We show that the proposed algorithm can be used to generate parsimonious segmentations and facilitate the computation of accurate mineralogical summaries for several simulated and real HSIs of terrestrial and planetary geological surfaces.