ICEpdf has had annotation creation tools for quite some time but they were never designed to support the PDF transparency model. This is further complicated by the fact the default java colour picker allows users to select rgba colour values but the PDF specification only allows the setting of rgb values (actually other colour models too but none with alpha).
Transparency was not possible in early version of the PDF specification and as a result to support legacy viewers the addition of alpha support had to be done in a way not to break backwards compatibility. As a result the extended graphics state was introduced and supporting viewers could implement the new transparency model and old viewers could simply ignore it.
New Feature
Major