Enhancing Underwater Gray Scale Images Using a Hybrid Approach of Filtering and Stretching Technique

Underwater image processing has received more attention from last few decades, underwater image quality is affected by several factors such as light attenuation, scattering, refraction, turbidity etc. because of this effect non uniform illumination, low contrast and blurring effect will arise in underwater images. The algorithm used in this paper uses both stretching and filtering technique to enhance the quality of underwater images and has been succeeded in correcting non uniform illumination, reduces noise and enhancing contrast. Here it uses histogram equalization and contrast stretching for enhancing the contrast, it uses a Homomorphic filter for uniform illumination and reduce Gaussian blur, wavelets are used for reducing Gaussian and salt and pepper noises, Anisotropic filtering is used for enhancing foreground(edges) and acts as low pass filter for background. Simulation is carried out using MATLAB (R2010b), visual quality and PSNR shows the improvement in quality of underwater images.