19 January 2009 Exposure-adaptive color-image enhancement
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Abstract
In many cases, it is not possible to faithfully capture shadow and highlight image data of a high dynamic range (HDR) scene using a common digital camera, due to its narrow dynamic range (DR). Conventional solutions tried to solve the problem with an captured image which has saturated highlight and/or lack of shadow information. In this situation, we introduce a color image enhancing method with the scene-adaptive exposure control. First, our method recommends an optimal exposure to obtain more information in highlight by the histogram-based scene analysis. Next, the proposed luminance and contrast enhancement is performed on the captured image. The main processing consists of luminance enhancement, multi-band contrast stretching, and color compensation. The luminance and chrominance components of input RGB data is separated by converting into HSV color space. The luminance is increased using an adaptive log function. Multi-band contrast stretching functions are applied to each sub-band to enhance shadow and highlight at the same time. To remove boundary discontinuities between sub-bands, the multi-level low-pass filtering is employed. The blurred image data represents local illumination while the contrast-stretched details correspond to reflectance of the scene. The restored luminance image is produced by the combination of multi-band contrast stretched image and multilevel low-pass filtered image. Color compensation proportional to the amount of luminance enhancement is applied to make an output image.
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Jae-Hyun Kwon, Jae-Hyun Kwon, Wonhee Choe, Wonhee Choe, Kangeui Lee, Kangeui Lee, SeongDeok Lee, SeongDeok Lee, } "Exposure-adaptive color-image enhancement", Proc. SPIE 7250, Digital Photography V, 72500V (19 January 2009); doi: 10.1117/12.806065; https://doi.org/10.1117/12.806065
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