  The problem of foreground material signature extraction in an intimate
(nonlinear) mixing setting is considered. It is possible for a foreground
material signature to appear in combination with multiple background material
signatures. We explore a framework for foreground material signature extraction
based on a patch model that accounts for such background variation. We identify
data conditions under which a foreground material signature can be extracted up
to scaling and elementwise-inverse variations. We present algorithms based on
volume minimization and endpoint member identification to recover foreground
material signatures under these conditions. Numerical experiments on real and
synthetic data illustrate the efficacy of the proposed algorithms.
