Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1989-06-08
1990-05-15
Shepperd, John W.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 13, 358160, H04N 964, H04N 591, H04N 1104
Patent
active
049262467
ABSTRACT:
Apparatus for processing a first signal representing a color component of a pixel of an image in which the signal defines the value of the color component as one of a first set of values defining a first scale of color component values. The apparatus comprises a first Look-up Table addressed by the color component value for generating a second signal representing a modified color component value chosen from a set of modified color component values defining a second scale coarser than the first scale. An adjustment circuit comprises a memory in which at least two sets of adjustment data are stored, each set being associated with a respective dither threshold representing respective differences, hereinafter referred to an aquantization errors, between the first and second signals when compared on the first scale of color component values, the data of each set defining an adjustment instruction for each possible quantization error, the adjustment instruction being related to the difference between the quantization error and the respective dither threshold. The adjustment circuit means receives the first signal so that the memory is addressed by a signal related to the quantization error and related to the position of the pixel in the image so as to generate an adjustment control signal associated with the quantization error and the dither threshold corresponding to the first signal pixel. A modifying circuit is responsive to the adjustment control signal generated by the adjustment circuit to adjust the second signal to generate a final output signal representing one of the second set of the color component values.
REFERENCES:
patent: 3259690 (1966-07-01), Oshima et al.
patent: 3975584 (1976-08-01), Gordon
patent: 4196452 (1980-04-01), Warren et al.
patent: 4568966 (1986-02-01), Lippel
Crosfield Electronics Limited
Shepperd John W.
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