Dong Yu Lihong Ma Guoxi Wang Hanqing Lu Adaptive spread-transform dither modulation using an improved luminance-masked threshold. 449-452 2008 ICIP http://dx.doi.org/10.1109/ICIP.2008.4711788 conf/icip/2008 db/conf/icip/icip2008.html#YuMWL08