Po-Ming Lee Wei-Hsuan Tsui Yun Teng Tzu-Chien Hsiao Affective pattern analysis of image in frequency domain using the Hilbert-Huang Transform. 667-670 2012 APCCAS https://doi.org/10.1109/APCCAS.2012.6419123 conf/apccas/2012 db/conf/apccas/apccas2012.html#LeeTTH12