1. A method for processing images acquired by an imaging system comprising image detectors with non-uniform transfer functions and irregular spatial locations, characterized in that it comprises: accumulating data from multiple images; defining an affinity graph which edges define pairs of detectors that measure related signal; performing statistical analysis on the accumulated data from each pair of detectors; and solving a system constructed from the results of the statistical analysis to estimate each detector transfer function, the set of which compose a calibration of the imaging system.