According to this paper: https://doi.org/10.1016/j.jviromet.2011.10.003
my look into HIS system more.
During image processing, the saturation channel (HIS system) of the scanned color image (Gonzalez and Woods, 2008) was used to extract labelled cells from the uneven background, as the superimposed shadow appeared to have a saturation value similar to the non-shadow background.
According to this paper: https://doi.org/10.1016/j.jviromet.2011.10.003
my look into HIS system more.