Digital data is rapidly embedded in color/grayscale digital data by
switching between a set of multi-level screens or quantizers. Each screen
can be tuned to maximize the quality of the digital data product on the
intended display medium, so that the quality of the displayed product
does not suffer. The data embedding method/algorithm of the invention
generally involves generating a set of multi-level screens, each of which
is generated by selecting a set of colors that comprise the colors that
can be output by that multi-level screen; screening the input digital
medium with the generated multi-level screens using a dither matrix and a
set of level matrices; and selecting, for each of select number of pixel
locations in the input digital medium, one of the level matrices, based
on a message symbol to be embedded at that pixel location, to create an
output.