Empirical mode decomposition based visual enhancement of underwater images

Most underwater vehicles are nowadays equipped with vision sensors. However, underwater images captured using optic cameras can be of poor quality due to lighting conditions underwater. In such cases it is necessary to apply image enhancement methods to underwater images in order to enhance visual quality as well as interpretability. In this paper, an Empirical Mode Decomposition (EMD) based image enhancement algorithm is applied to underwater images for this purpose. EMD has been shown to be particularly suitable for non-linear and non-stationary signals in the literature, and therefore provides very useful in real life applications. In the approach presented in this paper, initially each R, G and B channel of the color underwater image is separately decomposed into Intrinsic Mode Functions (IMFs) using EMD. Then, the enhanced image is constructed by combining the IMFs of each channel with different weights, so as to obtain a new image with increased visual quality. It is shown that the proposed approach provides superior results compared to conventional image enhancement methods such as contrast stretching.