Comparison of the performance of inverse transformation methods from OSA-UCS to CIEXYZ.

The Optical Society of America's Uniform Color Scales (OSA-UCS) is one of the color spaces that most closely approximate a "true" uniform color space. Different techniques have been used to convert OSA-UCS-based color specification parameters, L, j, and g, to the CIE tristimulus values, X, Y, and Z. However, none of these methods provides a direct method of inverting OSA-UCS to CIEXYZ values. Thus, numerical algorithms, such as the Newton-Raphson method, have been employed to obtain the transformations. The relative low accuracy and long computation time of this method makes it undesirable for practical applications. An artificial neural network (ANN) was employed to convert OSA-UCS to CIEXYZ. Its performance was compared with that of numerical methods. After optimization, ANN gave a better performance with a mean error (ΔEXYZ) of 1.0×10(-4) and a conversion time of less than 1 s for 1891 samples.