Apparatus and method for flexible digital halftoning are provided in which
novel pattern choices are allowed by not restricting the basic halftone
patterns to grow sequentially. Rather, positions in a threshold array
allow multiple transitions between on (i.e., printed with toner/ink) and
off (not printed) as a function of the input value at the corresponding
position. In one embodiment, multiple threshold matrices are employed and
the output decision is a vote (e.g., exclusive OR) of the outputs of the
individual threshold matrices. In another embodiment, each position
contains an arbitrary bit vector to express the output for each input.
This flexibility in growing basic halftone patterns allows the number of
densities output to be larger than n+1 (where "n" is the number of dots
within a basic halftone cell).