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Appl. Sci. 2018, 8(8), 1269;

Learning-Based Colorization of Grayscale Aerial Images Using Random Forest Regression

Department of Advanced Technology Fusion, Konkuk University, Seoul 05029, Korea
Department of Civil and Environmental Engineering, Seoul National University, Seoul 08826, Korea
Department of Technology Fusion Engineering, Konkuk University, Seoul 05029, Korea
Agency for Defense Development, Daejeon 34060, Korea
Author to whom correspondence should be addressed.
Received: 18 April 2018 / Revised: 10 July 2018 / Accepted: 27 July 2018 / Published: 31 July 2018
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Image colorization assigns colors to a grayscale image, which is an important yet difficult image-processing task encountered in various applications. In particular, grayscale aerial image colorization is a poorly posed problem that is affected by the sun elevation angle, seasons, sensor parameters, etc. Furthermore, since different colors may have the same intensity, it is difficult to solve this problem using traditional methods. This study proposes a novel method for the colorization of grayscale aerial images using random forest (RF) regression. The algorithm uses one grayscale image for input and one-color image for reference, both of which have similar seasonal features at the same location. The reference color image is then converted from the Red-Green-Blue (RGB) color space to the CIE L*a*b (Lab) color space in which the luminance is used to extract training pixels; this is done by performing change detection with the input grayscale image, and color information is used to establish color relationships. The proposed method directly establishes color relationships between features of the input grayscale image and color information of the reference color image based on the corresponding training pixels. The experimental results show that the proposed method outperforms several state-of-the-art algorithms in terms of both visual inspection and quantitative evaluation. View Full-Text
Keywords: colorization; random forest regression; grayscale aerial image; change detection colorization; random forest regression; grayscale aerial image; change detection

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Seo, D.K.; Kim, Y.H.; Eo, Y.D.; Park, W.Y. Learning-Based Colorization of Grayscale Aerial Images Using Random Forest Regression. Appl. Sci. 2018, 8, 1269.

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