A Study Of The Color Controlling Techniques For Digital Color Printers

Color management of digital color imaging devices enables colors consistent in an imaging system, and is widely used in many fields, such as textile, printing, and multimedia imaging. It has been being a hotspot for past ten years internationally. In various digital imaging equipments, output devices are the most complicated for their high level of system non-linearity. The paper puts on study of the color controlling techniques for digital output imaging devices. The aim is to learn and grip the key techniques of color management, and to lay a base for device developments and applications. The core of color management is device profile, which consists of device characterization, gamut description and gamut mapping. In this research, the output devices of different types were used. For the characterization, the tetrahedron interpolation method is used to build a three dimensional look-up table (3D-LUT). Approaches for sampling optimization and virtual increase in sampling volume are provided, improvement of the uniformity in output space and the bigger size of 3D-LUT have been obtained respectively. The conversion accuracy of the 3D-LUT is, therefore, more enhanced. In addition, a characterization means based on colorimetric density is proposed, which combines the concepts of physics models and the analytical models. The division of the procedure into 1_D and 3_D process significantly decreases the system complexity. The results prove that the two methods developed can convert colors more accurately. An imaging optimization is employed, which extracts the virtues of the two methods, resulting in an excellent image. In the gamut description study, the tetrahedron geometry knowledge is applied and the gamut boundaries are built by interpolation. The data used by interpolation are the same as that in characterization sampling. The quick acquiring of data interpolation with a gamut sphere is performed. The results indicate that the technique can be used in building up a gamut description and in gamut mapping algorithms. In this paper two gamut mapping algorithms were carried out. One is clipping mapping based on the nearest distance alone the equal lightness, which is the most effective for portrait and landscape images. The other is the GCUSP compression mapping, which is more effective for general kinds of images. Application experiments with three color printers show that the techniques in this paper are able to control output colors more effectively.