Image processing device and image processing method

An image processing method for processing an input image so as to reproduce a halftone, comprising:

• setting a threshold matrix having a plurality of elements arranged in M columns×N rows, at least two threshold values being stored in each of the elements;
• specifying a corresponding element of the threshold matrix in accordance with a position of a pixel in the input image;
• and
• fetching the threshold values from the specified element and generating a multilevel signal by transforming an input pixel value to one of multiple levels in accordance with the fetched threshold values;
• wherein in the generating of the multilevel signal, a constant value Doutmin is outputted as the multilevel signal when a first condition that the input pixel value is smaller than or not larger than a minimum value of the threshold values;
• a constant value Doutmax is outputted when a second condition that the input pixel value is larger than or not smaller than a maximum value of the threshold values, is satisfied;
• and an interpolation value between the two constant values Doutmin and Doutmax is outputted by carrying out a predetermined operation when both of the first condition and the second condition are not satisfied.

An image processing device comprising:

• an address generating section for generating an address data for each pixel in accordance with an input pixel value of a signal for the pixel and a position information for indicating a position of the pixel on an image;
• a plurality of lookup tables for outputting a plurality of values corresponding to the address data obtained by the address generating section;
• an interpolating operation section for generating one multilevel data by a predetermined interpolating operation in accordance with the plurality of output values obtained for each pixel and outputted from the plurality of lookup tables;
• a dot shift signal generating section for generating a dot shift signal by a pattern matching in accordance with the multilevel data obtained by the interpolating operation section;
• and
• a pulse signal generating section for generating a pulse signal for forming the image in accordance with the multilevel data and the dot shift signal;
• wherein the plurality of lookup tables store different reference data from each other.

An image processing method comprising:

• generating an address data for each pixel in accordance with an input pixel value of a signal for the pixel and a position information for indicating a position of the pixel on an image;
• extracting a plurality of values corresponding to the address data obtained in the generating of the address data, from a plurality of predetermined lookup tables;
• generating one multilevel data by a predetermined interpolating operation in accordance with the plurality of values obtained for each pixel and extracted from the plurality of lookup tables;
• generating a dot shift signal by a pattern matching in accordance with the multilevel data obtained in the generating of the multilevel data;
• and
• generating a pulse signal for forming the image in accordance with the multilevel data and the dot shift signal;
• wherein the plurality of lookup tables store different reference data from each other.