We propose a segmentation method based on Polya's urn model for contagious
phenomena. A preliminary segmentation yields the initial composition of an
urn representing the pixel. The resulting urns are then subjected to a modi
fied urn sampling scheme mimicking the development of an infection to yield
a segmentation of the image into homogeneous regions. This process is impl
emented using contagion urn processes and generalizes Polya's scheme by all
owing spatial interactions, The composition of the urns is iteratively upda
ted by assuming a spatial Markovian relationship between neighboring pixel
labels. The asymptotic behavior of this process is examined and comparisons
with simulated annealing and relaxation labeling are presented. Examples o
f the application of this scheme to the segmentation of synthetic texture i
mages, ultra-wideband synthetic aperture radar (UWB SAR) images and magneti
c resonance images (MRI) are provided.