Emmy-Noether Group

Perceptually Optimal Reproduction of Color Images considering Device Limits

In the proposed project the perceptually optimal reproduction of multispectral, high dynamic range images shall be investigated considering output-device limits (printers, displays and projectors). Of special interest are the limited metameric and spectral gamut as well as the low dynamic range of these devices. Previous approaches focused only on one single device limit (gamut mapping, spectral gamut mapping and HDR tone mapping). To allow for various appearance phenomena of the human visual system, however, a unified approach is necessary. For this purpose existing image appearance models shall be modified in order to map the image into a perceptually uniform appearance correlate space. One basic goal of this project is the development of a color difference measure within this space based on human spatial and color vision. For a multispectral image a sequence of coupled variational problems subject to device limits can be constructed by means of this image difference measure. The solution is an operator, which transforms the image into the device limits with minimal perceptual disagreement to the original. New numerical methods shall be developed to solve these variational problems. Particular importance shall be attached to their numerical complexity, convergence speed and robustness in order to handle also high resolution multispectral images in reasonable time. A prototypical multispectral reproduction system shall be designed and realized to show the feasibility of this approach, its applicability in terms of computational performance and to validate its optimality by means of psychophysical comparison experiments with existing methods.