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Proceedings Paper

Illuminant spectrum estimation using a digital color camera and a color chart
Author(s): Junsheng Shi; Hongfei Yu; Xiaoqiao Huang; Zaiqing Chen; Yonghang Tai
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Paper Abstract

Illumination estimation is the main step in color constancy processing, also an important prerequisite for digital color image reproduction and many computer vision applications. In this paper, a method for estimating illuminant spectrum is investigated using a digital color camera and a color chart under the situation when the spectral reflectance of the chart is known. The method is based on measuring CIEXYZ of the chart using the camera. The first step of the method is to gain camera′s color correction matrix and gamma values by taking a photo of the chart under a standard illuminant. The second step is to take a photo of the chart under an estimated illuminant, and the camera′s inherent RGB values are converted to the standard sRGB values and further converted to CIEXYZ of the chart. Based on measured CIEXYZ and known spectral reflectance of the chart, the spectral power distribution (SPD) of the illuminant is estimated using the Wiener estimation and smoothing estimation. To evaluate the performance of the method quantitatively, the goodnessfitting coefficient (GFC) was used to measure the spectral match and the CIELAB color difference metric was used to evaluate the color match between color patches under the estimated and actual SPDs. The simulated experiment was carried to estimate CIE standard illuminant D50 and C using X-rite ColorChecker 24-color chart, the actual experiment was carried to estimate daylight and illuminant A using two consumergrade cameras and the chart, and the experiment results verified feasible of the investigated method.

Paper Details

Date Published: 29 October 2014
PDF: 9 pages
Proc. SPIE 9273, Optoelectronic Imaging and Multimedia Technology III, 927307 (29 October 2014); doi: 10.1117/12.2071915
Show Author Affiliations
Junsheng Shi, Yunnan Normal Univ. (China)
Hongfei Yu, Yunnan Normal Univ. (China)
Xiaoqiao Huang, Yunnan Normal Univ. (China)
Zaiqing Chen, Yunnan Normal Univ. (China)
Yonghang Tai, Yunnan Normal Univ. (China)

Published in SPIE Proceedings Vol. 9273:
Optoelectronic Imaging and Multimedia Technology III
Qionghai Dai; Tsutomu Shimura, Editor(s)

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