Steerable local frequency based multispectral multifocus image fusion

•Steerable local frequency based focus measure.•Oriented analytic image for steerable local frequency using steerable filters.•Proposed focus measure shown to perform extremely well across different spectra.•Highly promising multispectral multifocus fusion.

Design of a focus measure and a fusion algorithm which will perform well across different spectra remains an extremely challenging task. In this work, the problem of multispectral multifocus image fusion is addressed using the phase information of the source image pixels at different orientations. We make the local frequency, the spatial derivative of the local phase of the pixels, steerable to obtain a good novel focus measure. Oriented analytic image based on the theory of steerable filters is constructed for that purpose. A multifocus fusion algorithm is proposed next using this focus measure. Comprehensive experimentations clearly demonstrate that our focus measure as well as the multifocus fusion algorithm yield promising results across the visual (VIS), the near-infrared (NIR) and the thermal (TH) spectra.