Image Quality Improvement of Underwater Images in Ideal HSI Color Space In the underwater circumstance, the light attenuates, and its attenuation rate depends on the wavelength. Long wavelength light is easily absorbed. Also, the light attenuation rate of blue and green component changes according to the water quality, thus, the white balance of images is lost. The attenuation of the light reduces colorfulness and contrast of images, furthermore, causes blurring. When photographing, the illumination becomes uneven for the subject, thus, brightness unevenness occurs in the acquired captured images. In this paper, an underwater image signal is converted to the ideal HSI color space and apply processing suitable for various deterioration factors to saturation and intensity independently. High quality improvement of underwater image was realized.

Underwater Image Enhancement Based on the Iteration of a Generalization of Dark Channel Prior Underwater image enhancement is important for images captured in underwater because underwater images often suffer from color cast, low contrast and degraded visibility due to the absorption and scattering of light in water. In this paper, we propose a novel algorithm for underwater image restoration based on a generalization of the dark channel prior (GDCP). Though there are various types of underwater images, we especially focus on underwater images with depth because these images are not enhanced well by current algorithms. The proposed algorithm is composed of the iteration of GDCP and image fusion. Additionally, we introduce the new ambient light estimation to adapt to more types of images. Experimental results show that proposed algorithm is effective for various types of underwater images, especially for the images with depth.