自然影像中複合光源之分析研究

A Study on the Analysis of Multiple Illuminants in a Natural Image

陳怡君(Chen Yi-Chun)

指導教授 ： 周遵儒

國立臺灣師範大學/科技學院/圖文傳播學系/碩士(2009年)

摘要

影像拍攝過程中，由於環境光源的影響易導致物體呈現不同的色彩，無法忠實地表現物體真實的顏色，使得無法辨識影像內物體與真實物體是否相同，因此，若欲呈現真實地色彩則必須控制環境光源。於環境光源控方面，可分為事前花費大筆成本建構標準拍攝環境空間；另外一方面，則可透過事後的色彩技術，估計其拍攝時環境光源進而還原出物體色彩。
　　本研究欲開發一套複合光源的分析方法：首先，本研究藉由色彩比例值進行物體反射譜的模擬。其次，在單一光源估計方面，透過色域極限點光源偵測法與不變色光源偵測法，將欲估計自然影像經過色彩空間轉換，根據與參考色位置的距離計算，找出該參考色對應到的光源，進而估計當時物體拍攝時的環境光源。最後，在複合光源分析方面，將運用影像分割判斷出影像中主光源的可能性。
　　希望藉由實驗結果，提高影像顯示的準確性，此結果預計將可應用於影像合成、數位典藏、醫學影像等數位影像後製過程，透過色彩修正處理，促使影像更符合真實現象。

關鍵字

物體反射譜 ； 光源 ； 色域

並列摘要

The impact of environmental light source leads into the object show a different color in the process of capture. That can not be faithful performance of the real color. So we can not know the object of image and the real object whether the same. Therefore, if we want to present true color, we must control environmental light source. That can spend substantial costs to construct standards environment space of capture before shooting, or through the color technology after shooting to estimate environment light source to further restore color of objects.
　　This study aimed to develop a method of analysis of multiple illuminants. First of all, we simulated spectral reflectance of objects that used by the proportion of color. Secondly, two methods of single illuminant estimation were derived, including gamut extreme light estimation and invariant color light estimation. We used the natural image via color space conversion to estimate single illuminant by calculating distance form the reference color. Finally, in the analysis of multiple illuminants, we used image segmentation to understand it changing circumstances then making out the main illuminant in the image.
　　We hope through experimental results improve the accuracy of image display. These results will be applied to color amendments of synthesis image, digital archives, medical imaging and other digital image post-production process to make it be more natural and more coordinative.

並列關鍵字

Spectral reflectance ； Illuminant ； Color gamut

參考文獻

[2]　V. Bochko, N. Tsumura, and Y. Miyake, “A Spectral Color Imaging System for Estimating Spectral Reflectance of Paint,” Journal of Imaging Science and Technology, Vol.51, No.1, pp.70-78, 2007.

[3]　諸葛慧(2006)。色溫調整影像合成技術之研究。國立台灣師範大學圖文傳播學系碩士論文。

[5]　International Organization for Standardization, “CIELAB Standard Colour Image Data,” ISO 12640-3, 2007.

[9]　M.J. Vrhel and H.J. Trussell, “Color Correction Using Principal Components,” Color Research and Application, Vol.17, No.5, pp.328-338, 1992.

[11] L.T. Maloney,” Evaluation of Linear Models of Surface Spectral Reflectance with Small Numbers of Parameters,” Journal of the Optical Society of America A, Vol.3, No.10, pp.1673-1683, 1986.