Loading patent…
AssigneeHitachi, Ltd.
InventorsTakeshi Shibuya, Tadashi Okada, Masayuki Kanda, Eiji Yoshino, Atsushi Onose, Tatsuki Inuzuka, Toshiaki Nakamura
Estimating the term…
In a halftoning unit of a laser printer and the like, a high speed, high density and high gradations halftoning is realized by multi-value implementation by clustered dot concentrated dither halftoning (known as a sub-matrix method) and PWM distributing gradation among the plurality of halftone dots with a small memory and circuit. For this purpose, the value of the difference between an input gradation value ni and a threshold value nc, Δn=ni−nc, is shortened within a range of 0 to Δh and the lower s bit of Δh is removed by a round-down or round-up process. Meanwhile, a threshold array is generated from an extended threshold pattern obtained by combining threshold patterns of 2s whose threshold interval is Δh, i.e. ΔAh×K, Δh×K+1, . . . , Δ×K+2(s−1). Thereby, a halftone dot dither process in which the PWM gradation increases distributively among the 2s dots may be realized with a small scale memory and circuit.
A halftoning unit comprising a threshold array converting an input gradation value ni of an input pixel of 8 bits (=256 levels) per pixel into an output gradation value which can be rendered with less bit width by sequentially comparing with a threshold value nc of the threshold array;
A printer comprising a threshold array for control of a multi-level output gradation value to an output minimum pixel by sequentially comparing an input gradation value ni of an inputted pixel of 8 bits (=256 levels) per pixel and a threshold value nc of the threshold array;
Dependencies are inferred from the claim text.