Reproduction spectrale de la couleur : approches par modélisation et par diffusion vectorielle de l'erreur
Résumé
My research concerns spectral color reproduction within printers. We will first briefly expose the field of work: multi-spectral imaging, problem of metamerism and kind of data we aim to reproduce in comparison to color reproduction. Ideally we would like to perform an exact reproduction of an original scene: no perceived differences by a human observer between an original scene and its spectral color reproduction while changing the illumination conditions. Then introducing our spectral color reproduction system, a multi-colorant ink-jet printer, we will look at the spectral response of this system in order to reproduce spectral data. Two approaches have been tested: model based and vector error diffusion. The first approach follows a similar workflow as color reproduction: gamut mapping, colorant separation and halftoning. Using a printer model we can establish the forward transformation from colorant combinations to printed spectral reflectances. We will then consider the inverse relation to properly control our printing system. In the second approach we directly perform halftoning on the spectral image by spectral vector error diffusion. This technique combines both the colorant separation and the halftoning operation in one step. Improvements to this halftoning have been proposed in order to reduce visible artifacts due to error accumulation during the diffusion. These two approaches allow to work in simulation and to estimate the spectral color reproduction for different sets of colorants. We will conclude by comparing the reproductions of spectral data obtained with these two approaches.
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