Journal of Imaging Science and Technology® 50(2): 125–138, 2006. © Society for Imaging Science and Technology 2006 Optimized RGB for Image Data Encoding Beat Münch and Úlfar Steingrímsson Swiss Federal Laboratories for Material Testing and Research (EMPA), Dübendorf, Switzerland E-mail:
[email protected] Indeed, image data originating from digital cameras and Abstract. The present paper discusses the subject of an RGB op- scanners are highly device dependent, and the same variabil- timization for color data coding. The current RGB situation is ana- lyzed and those requirements selected which exclusively address ity exists for image reproducing devices such as monitors the data encoding, while disregarding any application or workflow and printers. Figure 1 shows the locations of the primaries related objectives. In this context, the limitation to the RGB triangle for a few important RGB color spaces, revealing a manifold of color saturation, and the discretization due to the restricted reso- lution of 8 bits per channel are identified as the essential drawbacks variety. The respective specifications for the primaries, white of most of today’s RGB data definitions. Specific validation metrics points and gamma values are given in Table I. are proposed for assessing the codable color volume while at the In practice, the problem of RGB misinterpretation has same time considering the discretization loss due to the limited bit resolution. Based on those measures it becomes evident that the been approached by either providing an ICC profile or by idea of the recently promoted e-sRGB definition holds the potential assuming sRGB if no ICC profile is present.