Smoothness of color transformations
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- Institutt for design 
Color image quality is an important factor in various media such as digital cameras, displays and printing systems. The employment of different color imaging media leads to a constant problem that each device produces color differently. In this case the image reproduction quality depends on processes of device characterization. Color look-up tables (LUTs) are the most common empirical approach for device characterization, and are the basis for ICC profiles. Correct 3DLUT-based color conversion in device characterization is an important factor for achieving high quality of the reproduced color image. Such factors as LUTs size, interpolation methods and unavoidable noise in color measurement process and unstable printing process influence on smoothness of 3DLUT-based color transforms, and may result in the appearance of artifacts in the final reproduced images. It is quite common to evaluate the quality of color transforms in terms of colorimetric accuracy, but smoothness is often neglected, even through its importance is now generally agreed on (Olson, 1999). The main goal of this project was to find a way of quantifying to which extent different transforms smooth or not smooth output images through analysis of LUT-based device characterization process, investigating factors which affect on color transformations and testing different existed methods. There are some scientific studies dedicated to evaluating smoothness of color transforms but the proposed algorithms were applied and tested only on well-designed 3D-LUTs, device characterization process and experimental data. So these metrics still require testing and evaluation using complex images and on profiles obtained during different measurements and in different environments.