Abstract
To solve the color cast and low contrast of underwater images caused by the effects of light absorption and scattering, we propose a novel underwater image enhancement method via bi-interval histogram equalization. The proposed method consists of three main parts: color correction, contrast enhancement, and multiscale fusion. First, the color cast is eliminated by automatic white balancing. Then, homomorphic filtering is adopted to decompose the image into high-frequency information and low-frequency information, the high-frequency information is enhanced by the gradient field bi-interval equalization which enhances the contrast and details of the image, and the low-frequency information is disposed via gamma correction for adjusting the exposure. Finally, we adopt a multiscale fusion strategy to fuse the high-frequency information, high-frequency after bi-interval equalization, and low-frequency information based on contrast, saturation, and exposure. Qualitative and quantitative performance evaluations demonstrate that the proposed method can effectively enhance the details and global contrast of the image and achieve better exposedness of the dark areas, which outperforms several state-of-the-art methods.
Highlights
Over the past decade, the exploration and protection of marine resources have become a widespread concern of the international community because of the abundant resources of oceans, rivers, and lakes
Our method employs white balance for correction of underwater images, we adopt homomorphic filtering to decompose the image after white balance into high-frequency and low-frequency information, and our method uses gradient field bi-interval equalization to further enhance the detail edge of highfrequency information. en, low-frequency information is processed by gamma correction
To solve the problem that the histogram equalization of gradient image leads many pixels in nonedge region changing to the edge region, which results in enhancement, we proposed bi-interval histogram equalization to avoid the over enhancement
Summary
The exploration and protection of marine resources have become a widespread concern of the international community because of the abundant resources of oceans, rivers, and lakes. There are three main problems with underwater imaging due to the absorption and scattering of light in underwater environment: color cast, underexposure, and low contrast. Is paper adopts multiscale fusion strategy to solve the excessive enhancement caused by the enhancement method while enhancing the details and exposure in the dark areas of the image. In order to solve the low contrast of the underwater image, our method employs homomorphic filtering to enhance the image. En, in order to further enhance the detailed information of the dark area of the image, the gradient field bi-interval equalization enhancement is adopted in the high-frequency information, which enhances the contrast and details while causing excessive enhancement in some areas. Our method significantly enhances the detail and exposure in dark areas of the image (qualitative and quantitative comparison in Sections 4.3 and 4.4).
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