即時高品質之高動態範圍成像系統

利用多張不同曝光畫面合成單一高動態範圍(High Dynamic Range ; HDR)影像之技術已廣泛應用在數位相機與智慧型手機等消費性電子產品，但相關技術卻因為影像幀率(Frame rate)的條件限制，一直未被成功應用於動態視訊上。本論文提出從雙次拍攝產生一即時與高品質的高動態範圍影像應用。目前常見的高動態範圍影像演算法都是使用ㄧ序列不同曝光的低動態範圍(Low Dynamic Range ; LDR)影像來合成出一高動態範圍影像，然而此種方式很難應用在即時的動態視訊上。故如何用最少的影像來源以擷取到最高的動態範圍是一個很重要的議題。本論文僅利用雙次拍攝所得到的兩個不同曝光的影像來源「自動曝光(Auto-Exposed ; AE)」與「補償曝光(Ill-Exposed ; IE)」作為影像來源，必提出「曝光適應性的虛擬影像(Exposure-Adaptive Virtual Frame)」與「曝光適應性的來源加強(Exposure-Adaptive Source Enhancement)」來解決因為影像來源較少所造成的「色調不連續(Color-Continuity)」與「細節缺乏(Lack of Detail Information)」的問題。本論文並在FPGA上以硬體實現一即時與高品質之高動態範圍視訊。

關鍵字

色調映射；色調連續性；曝光適應的來源強化；曝光適應的虛擬影像；高動態範圍；高動態範圍生成

並列摘要

High-Dynamic-Range(HDR) synthesis is popular in consumer products such as digital cameras and smart phones to generate high-quality still pictures. However, these techniques are difficult to be applied on video, owing to the strict timing constraints (i.e. 1/30 sec for a typical frame rate) posed on the images sources of various exposure values for HDR synthesis. We present a method to implement a real-time and high-quality High Dynamic Range (HDR) video synthesis from a dual-shot images application. Most previous algorithms for merging HDR images from a set of Low Dynamic Range (LDR) images, usually more than 5 LDR images, with different exposures times. To capture the widest dynamic range possible with the smallest number of sources, it is an important issue. In our method, two images of the scene are taken with different exposure time by using dual-shot system, then we provide an exposure-adaptive concept to overcome some problem which caused by lack of sources. Exposure-adaptive virtual frame to solve the color-continuity problem, and exposure-adaptive source enhancement to solve the lack of detail information. The proposed architecture enables a high-quality and real-time HDR video flow for a full resolution at 60 frames per second.

並列關鍵字

Exposure-Adaptive Source Enhancement ； Exposure-Adaptive Virtual Frame ； High Dynamic Range ； HDR Synthesis ； Color-Continuity ； Tone Mapping

參考文獻

[Debevec-97]P. E. Debevec and J. Malik, “Recovering High Dynamic Range Radiance Maps from Photographs”, in Proc. SIGGRAPH, pp.369-378, 1997.

[Lapray-12]P. J. Lapray, B. Heyman, and D. Ginhac, “HDR-ARtiSt: An Adaptive Real-time Smart camera for High Dynamic Range imaging”, in IEEE Transactions on Circuit and Systems for Video Technology, 2012.

[Wang-10]T. H. Wang, C. W. Fang, M. C. Sung, and J. J. Lien, “Photography Enhancement Based on the Fusion of Tone and Color Mappings in Adaptive Local Region”, in IEEE Transactions on Image Processing, vol.19, 2012.

[Reinhard-02] E. Reinhard, M. Stark, P. Shirley, and J. Ferwerda, “Photographic tone reproduction for digital images,” in Proc. SIGGRAPH, 2002, pp. 267-276

[Chen-07] J. Chen, S. Paris, F. Duarnd, “Real Time Edge-Aware Image Processing With the Bilateral Grid,” ACM Trans. Graphics, vol. 26, no. 3, article 103, 2007

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即時高品質之高動態範圍成像系統

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