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Open AccessArticle

Improved Bilateral Filtering for a Gaussian Pyramid Structure-Based Image Enhancement Algorithm

by Chang Lin 1,2,3, Hai-feng Zhou 1,3,* and Wu Chen 1
1
Marine Engineering College and Key Laboratory of Fujian province Marine and Ocean Engineering, Jimei University, Xiamen, Fujian 361021, China
2
School of Mechanical and Electrical Engineering, Putian University, Putian 351100, China
3
Key Laboratory of Modern Precision Measurement and Laser Nondestructive Detection Colleges and Universities in Fujian Province, Putian 351100, China
*
Author to whom correspondence should be addressed.
Algorithms 2019, 12(12), 258; https://doi.org/10.3390/a12120258
Received: 7 November 2019 / Revised: 24 November 2019 / Accepted: 26 November 2019 / Published: 1 December 2019
To address the problem of unclear images affected by occlusion from fog, we propose an improved Retinex image enhancement algorithm based on the Gaussian pyramid transformation. Our algorithm features bilateral filtering as a replacement for the Gaussian function used in the original Retinex algorithm. Operation of the technique is as follows. To begin, we deduced the mathematical model for an improved bilateral filtering function based on the spatial domain kernel function and the pixel difference parameter. The input RGB image was subsequently converted into the Hue Saturation Intensity (HSI) color space, where the reflection component of the intensity channel was extracted to obtain an image whose edges were retained and are not affected by changes in brightness. Following reconversion to the RGB color space, color images of this reflection component were obtained at different resolutions using Gaussian pyramid down-sampling. Each of these images was then processed using the improved Retinex algorithm to improve the contrast of the final image, which was reconstructed using the Laplace algorithm. Results from experiments show that the proposed algorithm can enhance image contrast effectively, and the color of the processed image is in line with what would be perceived by a human observer.
Keywords: bilateral filtering; Gaussian down-sampling; luminance; enhancement; Retinex bilateral filtering; Gaussian down-sampling; luminance; enhancement; Retinex
MDPI and ACS Style

Lin, C.; Zhou, H.-F.; Chen, W. Improved Bilateral Filtering for a Gaussian Pyramid Structure-Based Image Enhancement Algorithm. Algorithms 2019, 12, 258.

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