Abed Farhad Moghareh, Amirshahi Seyed Hossein, Abed Mohammad Reza Moghareh
Department of Color Physics, Institute for Colorants, Paint & Coatings, Tehran, Iran.
J Opt Soc Am A Opt Image Sci Vis. 2009 Mar;26(3):613-24. doi: 10.1364/josaa.26.000613.
A linear interpolation method is applied for reconstruction of reflectance spectra of Munsell as well as ColorChecker SG color chips from the corresponding colorimetric values under a given set of viewing conditions. Hence, different types of lookup tables (LUTs) have been created to connect the colorimetric and spectrophotometeric data as the source and destination spaces in this approach. To optimize the algorithm, different color spaces and light sources have been used to build different types of LUTs. The effects of applied color datasets as well as employed color spaces are investigated. Results of recovery are evaluated by the mean and the maximum color difference values under other sets of standard light sources. The mean and the maximum values of root mean square (RMS) error between the reconstructed and the actual spectra are also calculated. Since the speed of reflectance reconstruction is a key point in the LUT algorithm, the processing time spent for interpolation of spectral data has also been measured for each model. Finally, the performance of the suggested interpolation technique is compared with that of the common principal component analysis method. According to the results, using the CIEXYZ tristimulus values as a source space shows priority over the CIELAB color space. Besides, the colorimetric position of a desired sample is a key point that indicates the success of the approach. In fact, because of the nature of the interpolation technique, the colorimetric position of the desired samples should be located inside the color gamut of available samples in the dataset. The resultant spectra that have been reconstructed by this technique show considerable improvement in terms of RMS error between the actual and the reconstructed reflectance spectra as well as CIELAB color differences under the other light source in comparison with those obtained from the standard PCA technique.
在给定的一组观察条件下，采用线性插值法从相应的色度值重建孟塞尔色卡以及ColorChecker SG色卡的反射光谱。因此，在这种方法中，已创建了不同类型的查找表（LUT）来连接色度数据和分光光度计数据，将其作为源空间和目标空间。为了优化算法，已使用不同的颜色空间和光源来构建不同类型的LUT。研究了所应用的颜色数据集以及所采用的颜色空间的效果。通过在其他标准光源组下的平均色差和最大色差来评估恢复结果。还计算了重建光谱与实际光谱之间的均方根（RMS）误差的平均值和最大值。由于反射率重建的速度是LUT算法中的一个关键点，因此还测量了每个模型在光谱数据插值上花费的处理时间。最后，将所建议的插值技术的性能与常见的主成分分析方法的性能进行了比较。根据结果，使用CIEXYZ三刺激值作为源空间比CIELAB颜色空间更具优势。此外，所需样本的色度位置是表明该方法成功与否的一个关键点。实际上，由于插值技术的性质，所需样本的色度位置应位于数据集中可用样本的色域内。与从标准主成分分析技术获得的结果相比，通过该技术重建的所得光谱在实际反射光谱与重建反射光谱之间的RMS误差以及在其他光源下的CIELAB色差方面显示出相当大的改进。
