**4. Conclusions**

In this paper, we present an image enhancement approach to assist colorblind people with a better viewing experience. An image re-coloring method based on eigenvector processing is proposed for robust color separation under color deficiency transformation. It is shown that the eigenvector of color vision deficiency is distorted by an angle in the *λ*, *Y-B*, *R-G* color space. The proposed method represents clearly subjective image quality and the objective evaluation. Compared to the existing techniques, our results of natural images with CVD simulation work very well in terms of RMS, HDR-VDP-2 and IRB-approved human test. Both the objective comparison with previous works and the subjective evaluation on human tests validate the effectiveness of the proposed technique.

**Author Contributions:** H.-Y.L. proposed the idea, formulated the model, conducted the research and wrote the paper. L.-Q.C. developed the software programs, performed experiments and data analysis, and wrote the paper. M.-L.W. helped with the human test experiments.

**Funding:** The support of this work is in part by the Ministry of Science and Technology of Taiwan under Grant MOST 106-2221-E-194-004 and the Advanced Institute of Manufacturing with High-tech Innovations (AIM-HI) from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan.

**Conflicts of Interest:** The authors declare no conflict of interest.
