The Retinex based improved underwater image enhancement
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The Retinex based improved underwater image enhancement Najmul Hassan1 · Sami Ullah1 · Naeem Bhatti1 Muhammad Zia1
· Hasan Mahmood1 ·
Received: 6 December 2019 / Revised: 21 August 2020 / Accepted: 27 August 2020 / © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The underwater images suffer from low contrast and color distortion due to variable attenuation of light and nonuniform absorption of red, green and blue components. In this paper, we propose a Retinex-based underwater image enhancement approach. First, we perform underwater image enhancement using the contrast limited adaptive histogram equalization (CLAHE), which limits the noise and enhances the contrast of the dark components of the underwater image at the cost of blurring the visual information. Then, in order to restore the distorted colors, we perform the Retinex-based enhancement of the CLAHE processed image. Next, in order to restore the distorted edges and achieve smoothing of the blurred parts of image, we perform bilateral filtering on the Retinex processed image. In order to utilize the individual strengths of CLAHE, Retinex and bilateral filtering algorithms in a single framework, we determine the suitable parameter values. The qualitative and quantitative performance comparison with some of the existing approaches shows that the proposed approach achieves better enhancement of the underwater images. Keywords Retinex · CLAHE · Bilateral filter · Underwater images
1 Introduction In applications such as military surveillance, shipping, underwater communication networks etc. the underwater image enhancement (UIE) has attracted attention of the research community [15, 20, 24]. In the process of digital image acquisition, the reflected component of light from an object is responsible for image formation. Traveling inside water, light is susceptible to reflection, refraction, scattering and absorption. The absorption factor depends upon the energy of the light wave [30]. The red component of light has large wavelength and possesses low energy, whereas, the green and blue components have short wavelengths and possess high energy [23]. As a result, the green and blue colors are the dominant components of the image captured underwater. In the underwater images, low contrast occurs due to variable attenuation of different light wavelengths and the color degradations are Naeem Bhatti
[email protected] 1
Department of Electronics, Quaid-i-Azam University, 45320, Islamabad, Pakistan
Multimedia Tools and Applications
introduced due to the nonuniform absorption of red, green and blue components [15, 21]. In order to restore and enhance the degraded underwater images, the techniques presented in literature are generally based on image enhancement methods [8, 9, 15, 32], image dehazing [9, 12, 31] and image restoration methods [14, 15, 30]. In order to estimate the transmission in underwater environment, Drews-Jr et al. adapted the dark channel prior (DCP) method for underwater environment called as underwater DCP (UDC
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