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US 4,903,123 AGranted
Image processing apparatus using inclined line screens to reduce Moire
AssigneeCanon Kabushiki Kaisha
InventorsNaoto Kawamura, Hidejiro Kadowaki
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Abstract
There is disclosed an apparatus for processing a halftone image into a digital dot image. There are generated plural dots for the data of each pixel so as to form line screens in such a manner that smallest ones of the dots among the pixels constitute a line screen while other dots constitute line screens inclined to the scanning direction, in order to reduce Moire fringe pattern.
Claims9
An image processing apparatus comprising:
- pixel data input means;
- process means for intermediate tone processing of the pixel data entered by said input means to generate reproduction signals for dot formation;
- and
- scanning means for effecting line scanning in accordance with the reproduction signals generated by said process means,
- wherein said process means is adapted to generate the reproduction signals in such a manner that plural microdots are formed for each pixel data and that a line screen is formed by a group of said plural microdots, and further in such a manner that, in response to pixel data of a predetermined uniform density, a line screen is formed by continuously connecting the smallest microdots among plural microdots in each pixel and the line screen formed by connecting the smallest microdots is oblique to the direction of said line scanning.
2 more elements
An image processing apparatus comprising:
- input means for inputting pixel data;
- and
- means for processing the pixel data input by said input means;
- said processing means having dither processing means for performing dither conversion of the pixel data in accordance with a dither matrix composed of plural kinds of basic cells of threshold values, each cell being of the same shape but having different arrangements of threshold values, said plural kinds of basic cells being alternately arranged in two orthogonal directions and being shifted relative to one another in row and column directions of said dither matrix by a and b, respectively, where a and b represent displacements between the plural kinds of basic cells, a and b each having a value other than zero;
- the dither matrix having a size N x N determined in accordance with N=m(a+b)+n(a-b) where m and n are minimum values of integers which satisfy m/n=(a+b)/(a-b);
- wherein said dither matrix has (l-1) threshold values for each input pixel data for forming microdots of a number (l-1) for each input pixel data;
- and
- wherein a relation:
- l=a/b.times.K+1
- is satisfied,
- in which l is an integer equal to or larger than 3, and K is a natural number.
8 more elements
Dependencies are inferred from the claim text.