色域對映在高動態成像和頻譜高傳真複印上的應用

Application of Gamut-Mapping between HDR Imaging and Multispectral Hi-Fi Color Reproduction

羅梅君(Mei-Chun Lo) ； 李文彬(Wen-Bin Li)

《中華印刷科技年報》 2016 (2016/04) Pp. 88-94

摘要

現今市面上各家廠商生產的顯示器並無統一的標準測試規範，顯示器的色域範圍(Gamut)都不一致，所以對於高動態範圍影像(High Dynamic Range Images)在進行跨媒體進行轉換時，就必須針對從可能『屬廣色域範圍』的原稿端到『屬較窄色域範圍』的複製端的成像設備，做最佳化的跨媒體色域對映運算，使影像在具不同大小色域範圍的成像媒體上，均能夠有較佳的色彩呈現效果。在本研究中之所以採用高動態範圍的影像來進行色域對映，乃在於『如何在窄色域範圍的顯示設備上，將高動態影像的細部層次保留下來，以維持其較優良的影像品質，視為相當大的研究挑戰』。

關鍵字

高動態成像 ； 色域對映 ； 多張影像融合 ； 頻譜複製 ； 軟式打樣

並列摘要

There is no unified standard display test specification on the market between manufacturers. Every output device’s gamut is different from others. Cross-media transform of HDR images (High –Dynamic-Range Images) needs to be visually reasonable and smooth via gamut mapping algorithms especially from an input device with a bigger color gamut to an output device having smaller gamut. Therefore, the aim of this research is to study the application of gamut mapping on HDR images, because both detail and gradation of HDR image can be satisfactorily rendered on an output/display device having smaller gamut is quite a considerable challenge on cross-media color reproduction systems/ market. Practically, viewing conditions can be disparately different from one another. This research, therefore, also took view conditions into account, and used CIECAM02 color appearance model to adjust output images according to the view condition of interest. As results, the output rendered images could be in compliance with all environmental aspects of the observer. In this research, the key focus was on cross-media gamut mapping applied on HDR. There were three main steps carried out in this study. First step was the set-up or construction of GBPs (Gamut Boundary Points) for both the input and the output devices considered. The next step was the process of HDR imaging, include a multiple image fusion and a HDR-like imaging. Finally the last step was to optimize the HDR type of cross-media color transform. Two type of output imaging devices were characterized and applied for these testing. One was a soft-proofing of CMYKOG High-Fidelity (Hi-Fi) printer, characterized using a multispectral approach. Another was a display, formatted with the standard of Adobe RGB color space. The experimental results showed that, by these three optimization steps of processing, those soft-copy image, which were rendered from either process of both the multiple-images confusion and HDR-like imaging, could gave visually satisfactory color appearance with pleasing details and gradations.

並列關鍵字

HDR imaging ； Gamut mapping ； Multiple images fusion ； Hi-Fi printing ； Soft proofing

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