  We introduce a distinct method to perform spatially-resolved spectral
analysis of astronomical sources with highly structured X-ray emission. The
method measures the surface brightness of neighbouring pixels to adaptively
size and shape each region, thus the spectra from the bright and faint
filamentary structures evident in the broadband images can be extracted. As a
test case, we present the spectral analysis of the complete X-ray emitting
plasma in the supernova remnant Puppis A observed with XMM-Newton and Chandra.
Given the angular size of Puppis A, many pointings with different observational
configurations have to be combined, presenting a challenge to any method of
spatially-resolved spectroscopy. From the fit of a plane-parallel shocked
plasma model we find that temperature, absorption column, ionization time
scale, emission measure and elemental abundances of O, Ne, Mg, Si, S and Fe,
are smoothly distributed in the remnant. Some regions with overabundances of
O-Ne-Mg, previously characterized as ejecta material, were automatically
selected by our method, proving the excellent response of the technique. This
method is an advantageous tool for the exploitation of archival X-ray data.
