Literature Review on Underwater Image Restoration Techniques

Underwater image restoration is a complex task due to lack of reference image and varying underwater environment. These images are degraded by absorption and scattering effect of light propagation. In water light undergoes wavelength dependent attenuation thus red light (longer wavelength) attenuates faster than blue light. As depth increase, light drops most of the red content and image appears in bluish-green color tone. These images also suffer from low contrast, color cast and hazy appearance. Existing methods may require specialized hardware or it may be based on multiple images of same scene. Thus they cannot be used in real time or video acquisition task. Therefore it is desirable to develop an effective method to restore color and enhance contrast of these images. As goes deeper into water the blurriness in the image increases and this prior is used to obtain depth map. The backlight is obtained based on image blurriness and variance. These factors are substituted in the image formation model (IFM) to restore the image.