A review on image enhancement and color correction techniques for underwater images

Degradation of underwater images is different from normal images. In underwater imaging light interact with water in two ways, scattering and absorption. The scattering and absorption together is called attenuation of light in water. This attenuation is wavelength dependent. Because of scattering and absorption, underwater images are affected by back scattering, forward scattering and absorption of light in water. As a result of which the images are degraded, and also dominated by green or blue color. Water is not only source of degradation, but underwater images are also affected by suspended particles and dissolved compounds in water. The degradation also depends upon depth of water, day time, geographical location, source of light and physical properties of water etc. Many underwater applications need clear underwater images. Clear underwater images can be achieved by image enhancement and restoration techniques. The image enhancement techniques are simpler and faster than restoration processes because it does not require any prior knowledge about the parameters of water, where image has been captured. Underwater image enhancement techniques includes contrast enhancement, non uniform illumination correction, and color correction techniques. Among these very few researchers attempted a problem of non uniform illumination correction. Some image enhancement and color correction techniques for underwater images are reviewed in this paper. The quality metrics used to test the image quality are also discussed in the paper.