Improved color reproduction based on CIELAB color space in integrated multi-scale retinex

Abstract

Recently, tone reproduction is widely used in the field of image enhancement and HDR imaging. This method is especially used to provide the proper luminance so that captured images give the same sensation as the scene. As a result, we can get high contrast and naturalness of colors. There is ample literature on the topic of tone reproduction that has the objective of reproducing natural looking color in digital images. In recent papers, IMSR (Integrated multi-scale Retinex) shows great naturalness in the result images. Most methods, including IMSR, work in RGB or quasi-RGB color spaces, although some method adopted the use of luminance. This raises hue distortion from the point of the human visual system, that is, hue distortion in CIELAB color space. Accordingly, this paper proposes an enhanced IMSR method in a device-independent color space, CIELAB, to preserve hue and obtain high contrast and naturalness. In order to achieve the devised objectives, a captured sRGB image is transformed to the CIELAB color space. IMSR is then applied to only L * values, thus the balance of colors components are preserved. This process causes unnatural saturation, therefore saturation adjustment is performed by applying the ratio of chroma variation at the sRGB gamut boundary according to the corrected luminance. Finally, the adjusted CIELAB values are transformed to sRGB using the inverse transform function. In the result images of the proposed method, containing both high and low luminance regions, visibility in dark shadow and bright regions was improved and color distortion was reduced.

An Improved Retinex Image Enhancement Technique for Dim Target Extraction in Infrared Images

“…So far, many traditional and advanced enhancement techniques have been proposed to improve the quality of image in complex lighting conditions, such as the histogram equalization, the adaptive histogram equalization technique [6] and a variety of retinex theory based algorithms [7,8,9,10,11]. Among them, because retinex based methods are derived from Land's Retinex theory as a model of human vision system, these methods are considered as an effective method to enhance the dim infrared target.…”