Xiao Kaida, Zhu Yuteng, Li Changjun, Connah David, Yates Julian M, Wuerger Sophie
Opt Express. 2016 Jun 27;24(13):14934-50. doi: 10.1364/OE.24.014934.
A improved spectral reflectance reconstruction method is developed to transform camera RGB to spectral reflectance for skin images. Rather than using conventional direct or two-step processes, we transform camera RGB to skin reflectance directly using a principal component analysis (PCA) approach. The novelty in our direct method (RGB to spectra) is the use of a skin-specific colour characterisation chart with spectra closer to human skin spectra, and a new database of skin reflectances to derive the PCA bases. The experimental results using the facial images of 17 subjects demonstrate that our new direct method gives a significantly better performance than conventional, two-step methods and direct methods with traditional characterization charts. This new spectral reconstruction algorithm is sufficiently precise to reconstruct spectral properites relating to chromophores and its performance is within the acceptable range for maxillofacial soft tissue prostheses (error < 3 ΔE* units).
一种改进的光谱反射率重建方法被开发出来，用于将相机RGB转换为皮肤图像的光谱反射率。我们不是使用传统的直接或两步法，而是使用主成分分析（PCA）方法直接将相机RGB转换为皮肤反射率。我们直接方法（RGB到光谱）的新颖之处在于使用了一个光谱更接近人类皮肤光谱的皮肤特定颜色特征图，以及一个新的皮肤反射率数据库来推导PCA基。使用17名受试者面部图像的实验结果表明，我们的新直接方法比传统的两步法和使用传统特征图的直接方法具有显著更好的性能。这种新的光谱重建算法足够精确，能够重建与发色团相关的光谱特性，并且其性能在颌面软组织假体的可接受范围内（误差<3ΔE*单位）。
