Essay Example on DWT Towards Appearance Enhancement of Underwater Images

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DWT Towards Appearance Enhancement of Underwater Images Abstract Processing of underwater images has received a great attention among the researchers in recent years In oceanic environment capturing a clear underwater image is having a crucial importance Absorption and scattering are the major degrading factors for underwater images The qualities of underwater images are affected by color cast poor visibility and foggy appearance and misty In order to overcome those limitations an underwater image enhancement technique built on a DWT method is proposed The aim of the proposed algorithm is to improve the quality of underwater images In this paper 100 different images are used to perform the comparison of the proposed technique with the previous techniques Performance of the proposed method of DWT is evaluated using the Structural Similarity Index SSIM Entropy and Absolute Mean Brightness Error AMBE Performance measurement of the Wavelet techniques produces better enhancement results than previous techniques like Histogram Equalization HE and Contrast Limited Adaptive Histogram 



Equalization CLAHE Keywords Image enhancement DWT Color Cast CLAHE HE 1 INTRODUCTION Underwater image processing is challenging due to the physical properties of underwater environment In many cases captured underwater images are corrupted by absorption and scattering Additionally the underwater image brings unwanted noise and increases the effects of scattering The degree of absorption depends on different wavelengths of light red blue green which leads to the color cast of underwater images In this there are two kinds of scattering first one is forward scattering that leads to blurring and second one is backward scattering that causes low contrast Capturing a clear and high quality underwater image is not an easy work since underwater images are suffers from the above properties However there are many image base methods in underwater image enhancement Local and global image contrast enhancement is widely used to improve the visibility of underwater images Improving the underwater image quality can be divided into two different problems They are the image restoration problem and the image enhancement problem Underwater images are essentially characterized by their poor appearance because the lights are travels in the water and the outputs are poorly contrasted and hazy

Absorption and scattering effects are due to not only to the water itself but also to other components such as dissolved organic matter or some floating particles The visibility ranges are increased by using the artificial lighting Finally the amount of light is decreased when we go in depth into the sea and colors are drop off one by one depending on their wavelengths The blue color travels the long distance in the water due to its shortest wavelength and making the underwater images to be dominated essentially by the blue color Chong Yi Li Ji Chang Guo et al 2016 1 proposed a new method for enhancing the underwater images A systematic underwater image enhancement method which includes an underwater image dehazing algorithm and a contrast enhancement algorithm is proposed An effective contrast enhancement algorithm is proposed based on a kind of histogram distribution prior which increases the contrast and brightness of underwater images Miao Yang Member and Arcot Sowmya 2015 2 proposed a new method for enhancing the underwater images In this paper UCIQE is an effective metric to measure the image enhancement results Color Image Quality Index CIQI is a linear combination of colorfulness sharpness and contrast metrics Color Quality Enhancement CQE is measured with different colorfulness sharpness and contrast metrics Color Root Mean Enhancement CRME is used to measure the relative difference of the color cube centre and all the neighbours in the current color cube The UCIQE gives the best result when compare to the CIQI CQE and CRME Yafei Wang Xueyan Ding et al 2017 3 have discussed a new method specifically developed for image enhancement In this paper an efficient fusion based underwater image enhancement approach using wavelet decomposition is presented The fusion process involves two inputs which are represented as color corrected and contrast enhanced images these are extracted from original underwater image

Both the color corrected and contrast enhanced images are decomposed into low and high frequency components by using three scale wavelet operator The low and high frequency components are fused through a multiscale fusion process The low frequency components are fused by weighted average and the high frequency components are fused by local variance The fused low and high frequency components can be reconstructed as final enhanced image Finally the proposed algorithm can improve the appearance of underwater images John Y Chiang and Ying Ching Chen 2012 4 have discussed a new method specifically developed for image enhancement In this paper the WCID algorithm is proposed to restore the image color balance and remove haze In Histogram equalization method and dehazing the removal of haze color balancing capabilities and image dehazing WCID are traditional Ali A Yassin Rana M Ghadban et al 2013 6 proposed a new method for enhancing the underwater Images In this paper a new approach is presented which depends on DWT HSV color space and slide stretching The Input image is transformed to the HSV and the DWT is applied on the H channel Apply contrast stretching on H channel Then stretched the transform of Hue channel to spatial domain stretched the saturation and value channel Then


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