Abstract
Since underwater imaging is affected by the complex water environment, it often leads to severe distortion of the underwater image. To improve the quality of underwater images, underwater image enhancement and restoration methods have been proposed. However, many underwater image enhancement and restoration methods produce over-enhancement or under-enhancement, which affects their application. To better design underwater image enhancement and restoration methods, it is necessary to research the underwater image quality evaluation (UIQE) for underwater image enhancement and restoration methods. Therefore, a subjective evaluation dataset for an underwater image enhancement and restoration method is constructed, and on this basis, an objective quality evaluation method of underwater images, based on the relative symmetry of underwater dark channel prior (UDCP) and the underwater bright channel prior (UBCP) is proposed. Specifically, considering underwater image enhancement in different scenarios, a UIQE dataset is constructed, which contains 405 underwater images, generated from 45 different underwater real images, using 9 representative underwater image enhancement methods. Then, a subjective quality evaluation of the UIQE database is studied. To quantitatively measure the quality of the enhanced and restored underwater images with different characteristics, an objective UIQE index (UIQEI) is used, by extracting and fusing four groups of features, including: (1) the joint statistics of normalized gradient magnitude (GM) and Laplacian of Gaussian (LOG) features, based on the underwater dark channel map; (2) the joint statistics of normalized gradient magnitude (GM) and Laplacian of Gaussian (LOG) features, based on the underwater bright channel map; (3) the saturation and colorfulness features; (4) the fog density feature; (5) the global contrast feature; these features capture key aspects of underwater images. Finally, the experimental results are analyzed, qualitatively and quantitatively, to illustrate the effectiveness of the proposed UIQEI method.
Highlights
As an essential carrier and expression form of underwater information, underwater imaging has played a critical role in the development of research for the ocean, such as the three-dimensional reconstruction of seabed scenes [1], marine ecological monitoring, autonomous underwater vehicle, and remote underwater vehicle navigation [2,3].the complex underwater environment seriously affects the quality of underwater images, such as low visibility, blur texture, color distortion, and noise
A new underwater image quality assessment (UIQE) database is established, which contains 405 enhanced and restored underwater images. These images are generated from 45 different underwater real images and enhanced by 9 representative underwater image enhancement methods
UIQE index (UIQEI) has been verified on the constructed underwater image quality evaluation (UIQE) database
Summary
As an essential carrier and expression form of underwater information, underwater imaging has played a critical role in the development of research for the ocean, such as the three-dimensional reconstruction of seabed scenes [1], marine ecological monitoring, autonomous underwater vehicle, and remote underwater vehicle navigation [2,3]. To better design underwater image enhancement and restoration methods, it is necessary to evaluate their quality. To better design underwater image enhancement and restoration methods, it is necessary to study the objective quality evaluation method for underwater image enhancement and restoration. We propose a new objective quality measurement method of the enhanced and restored underwater images, based on the underwater dark channel prior (UDCP) and the underwater bright channel prior (UBCP), which can effectively evaluate the quality of the enhanced and restored underwater images. The enhanced and restored underwater images usually show different degrees of degradation in the different local regions, which brings great difficulties to the overall quality recognition of enhanced and restored underwater images To solve this problem, an underwater dark channel map was used to illustrate the information of darker areas.
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