In *Proceedings of the 17th International Conference on Pattern Recognition (ICPR-2004)*, pages 181–185, August, 2004.

Paper doi abstract bibtex

Paper doi abstract bibtex

Colour correction is the problem of mapping device dependent RGBs to standard CIE XYZs. Traditionally it is solved for by an error minimising one-to-one linear transform. However this problem is ill-posed. There exist multiple reflectances, known as metamers, which induce the same RGB but different XYZs (and vice versa). In this paper, we propose that this ill-posedness might be viewed positively. Indeed, that it leads to an error-less transform for colour correction. We propose that a mapping is error-less if it takes an RGB to an XYZ such that there exists a real reflectance spectrum which integrates to this RGB-XYZ pair. We show how we can solve for a mapping which satisfies this error-less criterion. As in previous studies, we seek a linear transform that is error-less. We show that we can solve for such a transform by quadratic programming. Experiments demonstrate 3 important results. First, that a linear least squares transform is not error-less. Specifically, saturated RGB-XYZ pairs do not correspond to a plausible reflectance. Second, there exists a linear transform that is error-less. Finally, that the best error-less transform performs almost as well as least-squares, but substantially better for saturated colours. It is possible to map RGB to XYZ with zero error.

@inproceedings{uea22102, month = {August}, author = {G. D. Finlayson and P. M. Morovic}, booktitle = {Proceedings of the 17th International Conference on Pattern Recognition (ICPR-2004)}, title = {Error-less colour correction}, journal = {Proceedings of the 17th International Conference on Pattern Recognition (ICPR-2004)}, doi = {10.1109/ICPR.2004.1334498}, pages = {181--185}, year = {2004}, url = {https://ueaeprints.uea.ac.uk/id/eprint/22102/}, abstract = {Colour correction is the problem of mapping device dependent RGBs to standard CIE XYZs. Traditionally it is solved for by an error minimising one-to-one linear transform. However this problem is ill-posed. There exist multiple reflectances, known as metamers, which induce the same RGB but different XYZs (and vice versa). In this paper, we propose that this ill-posedness might be viewed positively. Indeed, that it leads to an error-less transform for colour correction. We propose that a mapping is error-less if it takes an RGB to an XYZ such that there exists a real reflectance spectrum which integrates to this RGB-XYZ pair. We show how we can solve for a mapping which satisfies this error-less criterion. As in previous studies, we seek a linear transform that is error-less. We show that we can solve for such a transform by quadratic programming. Experiments demonstrate 3 important results. First, that a linear least squares transform is not error-less. Specifically, saturated RGB-XYZ pairs do not correspond to a plausible reflectance. Second, there exists a linear transform that is error-less. Finally, that the best error-less transform performs almost as well as least-squares, but substantially better for saturated colours. It is possible to map RGB to XYZ with zero error.} }

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