Assessment of RGB Encoding for Color Imaging

This work presents validation measures for the optimization of RGB color data encoding. Various RGB specifications had been promoted in the past for standard use in imaging, most of them adapted to application or equipment specific requirements. Although some, as sRGB for instance, are already widely used, none of them has been accepted yet as a universal standard. All of them are subject to limitations regarding to the spatial scope of the color space, making it impossible to satisfy any required conditions in general. At present, a big variety of different RGB specifications for digital imaging might easily lead to color misinterpretations, because the specific RGB specifications are often missing in the image data. If either the locations of the primary colors or the gamma values are mixed up, color deficiencies are unavoidable. Since the acceptance of a global standard could help to eliminate potential confusions, attempts for the promotion of universal RGB specifications are frequently accomplished. In the present study, the specific requirements of an RGB in respect of the coding range are examined. A concept for quantitative examination of the encodable color space extent considering the visually perceivable resolution is proposed. Different types of parameters are gathered. First, the fraction of all physically feasible surface colors contained in a certain RGB space is accounted. Next, the visibility of the quantization due to the restricted resolution of the RGB coding is measured in terms of ∆E76. Finally, some widely used RGB definitions are analyzed and assessed on the basis of this evaluation scheme.