CIE chromaticity, Planckian locus, and correlated color temperature estimation from raw image data using color checker training images

Touraj Tajbakhsh

doi:10.1117/12.908349

21 February 2012 CIE chromaticity, Planckian locus, and correlated color temperature estimation from raw image data using color checker training images

Touraj Tajbakhsh

Author Affiliations +

Proceedings Volume 8292, Color Imaging XVII: Displaying, Processing, Hardcopy, and Applications; 82920L (2012) https://doi.org/10.1117/12.908349
Event: IS&T/SPIE Electronic Imaging, 2012, Burlingame, California, United States

Abstract

In this paper we discuss and quantitatively evaluate the mapping of raw sensor chromaticities, i.e., r = R/(R + G+B) and b = B/(R+G+B), into the CIE 1931 xy chromaticity space, with the constraint that solely training chromaticities are being used which have been obtained using a color checker at a certain illumination. The region near the Planckian locus is considered to be most relevant and a least-squares weighting scheme is proposed to minimize the residuals in this region. Furthermore, the Planckian and daylight loci are approximated in the rb raw sensor chromaticity space using color checker chromaticities at three illuminations, those commonly available in light-booths. The effect of daylight emulation compared to the standard daylight illumination is evaluated. In another part of this paper the mapping of rb chromaticities to correlated color temperature is discussed and evaluated. The proposed method is based on a weighted least-squares fit of a 2nd-order 2D polynomial and outperforms two other estimation methods. We present a comprehensive set of simulation results with real measurements of reflectance, sensitivity, and emission spectrums.

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Touraj Tajbakhsh "CIE chromaticity, Planckian locus, and correlated color temperature estimation from raw image data using color checker training images", Proc. SPIE 8292, Color Imaging XVII: Displaying, Processing, Hardcopy, and Applications, 82920L (21 February 2012); https://doi.org/10.1117/12.908349

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