MTF-tailored multi-resolution analysis for fusion of multi-spectral and panchromatic images

This work presents a multi-resolution framework for merging a multi-spectral image having an arbitrary number of bands with a higher-resolution panchromatic observation. The fusion method relies on the generalised Laplacian pyramid (GLP), which is a multi-scale oversampled structure. The goal is to selectively perform injection of spatial-frequencies from an image to another with the constraint of thoroughly retaining the spectral information of the coarser data. The novel idea is that a model of the modulation transfer functions (MTF) of the multi-spectral scanner is exploited to design the GLP reduction filter. Thus, the inter-band structure model (IBSM), which is calculated at the coarser scale, where both MS and Pan data are available, can be extended to the finer scale, without the drawback of the poor enhancement occurring when MTFs are assumed to be ideal filters. Experiments carried out on QuickBird data demonstrate that a superior spatial enhancement, besides the spectral quality typical of injection methods, is achieved by means of the MTF-adjusted fusion.