Intensity histogram equalisation, a colour-to-grey conversion strategy improving photogrammetric reconstruction of urban architectural heritage

The paper presents a novel technique for the conversion of the colour signal into a grey-level signal tailored to the 3D reconstruction of urban scenes. The presented approach, named IHE from Intensity Histogram Equalization, derives from previous methods. The proposed approach takes as input a set of images showing the same urban object possibly captured under different conditions and by different cameras. Then it processes the input images by maximizing the peaks of their chromatic channel distributions, in order to preserve the chromatic in-formation as much as possible. IHE has been evaluated by comparing its performance with that of other state-‐of-‐the-‐art algorithms in terms of 3D reconstruction. The experiments, carried out on two datasets, show that IHE generally outperforms the other approaches.