UWIT: underwater image toolbox for optical image processing and mosaicking in MATLAB

This paper shows results from our development of an extended MATLAB image processing toolbox, which implements some useful optical image processing and mosaicking algorithms found in the literature. We surveyed and selected algorithms from the field which showed promise in application to the underwater environment. We then extended these algorithms to explicitly deal with the unique constraints of underwater imagery in the building of our toolbox. As such, the algorithms implemented include: contrast limited adaptive histogram specification (CLAHS) to deal with the inherent nonuniform lighting in underwater imagery, Fourier based methods for scale, rotation, and translation recovery which provide robustness against dissimilar image regions, local normalized correlation for image registration to handle the low-feature, unstructured environment of the seafloor, multiresolution pyramidal blending of images to form a composite seamless mosaic without blurring or loss of detail near image borders. In this paper we highlight the mathematical formulation behind each of these algorithms using consistent notation and a unified framework. We depict some of our MATLAB toolbox results with an assortment of underwater imagery.