以Homomorphic濾波及細節加強做多重曝光影像融合

高動態範圍影像技術主要是從多張不同曝光度的低動態範圍影像，合成一張擁有較多場景細節的高動態範圍影像。在本論文中，提出一種多重曝光影像使用homomorphic filtering與細節加強的融合方法。本論文所提出的方法包含六個步驟。首先，考慮非線性亮度的人類視覺系統，使用頻率域的homomorphic filtering來達到亮度強化，並使用色彩校正做非線性的色彩補償。使用“cross-image” median filter 來消除低動態影像中的過度曝光與曝光不足區域以獲得一張供權重圖計算使用的參考亮度影像。再使用guided filter 與weighted least squares (WLS) optimization分別擷取出區域與全域細節部分。接著，權重圖的計算上包含空間域與跨影像的兩種計算模式，並使用cross bilateral filter來增加權重圖的準確性。最後，使用multiresolution spline based scheme 來達到影像融合並生成一張高動態範圍的結果影像。根據實驗結果顯示，本論文所提之研究方法較優於四個現有的方法。

關鍵字

相機響應函數；多重曝光影像融合；低動態範圍影像；高動態範圍影像；色調映射； homomorphic濾波

並列摘要

The main aim of high dynamic range (HDR) imaging is to use multiple low dynamic range (LDR) images with different exposures to generate an HDR image containing scene details. In this study, a multiexposure image fusion using homomorphic filtering and detail enhancement approach is proposed. The proposed approach contains six stages. First, considerong nonlinear intensity perception of the human visual system (HVS), intensity enhancement is achieved by using the homomorphic filter in the frequency domain and color correction is employed to perform gamma correction and nonlinear compensation for saturation loss. The “cross-image” median filter is used to eliminate over-exposed or under-exposed regions in LDR images to obtain a reference intensity image, which is used to estimate the weighting map. The guided filter and weighted least squares (WLS) optimization are used to perform local and global detail extractions, respectively. Then, weighting map estimations of spatial and cross-image consistency are performed and the cross bilateral filter is used to refine the final weighting map. Finally, the multiresulution spline based scheme is used to perform image fusion and generate the final HDR image. Based on the experimental results obtained in this study, the performance of the proposed approach is better than those of four comparison approaches.

並列關鍵字

tone mapping ； camera response function ； multiexposure image fusion ； low dynamic range image ； high dynamic range image ； homomorphic filtering

參考文獻

[35] S. Raman and S. Chaudhuri, “Bilateral filter based compositing for variable exposure photography,” in Proc. of Eurographics, 2009, pp. 1-4.

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以Homomorphic濾波及細節加強做多重曝光影像融合

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