Image forming apparatus, image forming method, and image forming program product for processing pixels of vertical and diagonal lines expressed by input multi-value pixel data

An image forming method comprising:

• forming an image based on input multi-value pixel data formed by an input data value or output multi-value pixel data formed by an output data value;
• converting the input multi-value pixel data into status values based on an achromatic threshold and a maximum color threshold, wherein each of the status values corresponds to one of at least three kinds of status values comprising an achromatic status value, a maximum color status value, and a halftone status value;
• determining a first target reference look-up table from among plural reference look-up tables by using a table including a column of a three pixel arrangement, a column of pixel arrangement descriptions and a column of reference look-up table identifiers and based on an arrangement of the status values of a target pixel and adjacent pixels in a pixel window, each of the plural reference look-up tables indicating an association between the arrangement of the status values of the pixels in the pixel window and an output data value for forming the output multi-value pixel data, wherein the pixels arranged in the pixel window correspond to the status values, and comprise the target pixel and a number of the adjacent pixels provided on both sides of the target pixel, the pixel window comprising three pixels in a main scanning direction and one or more pixels in a sub scanning direction;
• and changing the input data value of the input multi-value pixel data, into the output data value of the first target reference look-up table to form the output multi-value pixel data, and outputting the output multi-value pixel data for use at the image forming step.

An image forming program product comprising instructions for causing a computer to:

• form an image based on input multi-value pixel data formed by an input data value or output multi-value pixel data formed by an output data value;
• convert the input multi-value pixel data into status values based on an achromatic threshold and a maximum color threshold, wherein each of the status values corresponds to one of at least three kinds of status values comprising an achromatic status value, a maximum color status value, and a halftone status value;
• determine a first target reference look-up table from among plural reference look-up tables by using a table including a column of a three pixel arrangement, a column of pixel arrangement descriptions and a column of reference look-up table identifiers and based on an arrangement of the status values of a target pixel and adjacent pixels in a pixel window, each of the plural reference look-up tables indicating an association between the arrangement of the status values of the pixels in the pixel window and an output data value for forming the output multi-value pixel data, wherein the pixels arranged in the pixel window correspond to the status values which are converted at the converting from the input multi-value pixel data, and comprise the target pixel and a number of the adjacent pixels provided on both sides of the target pixel, the pixel window comprising three pixels in a main scanning direction and one or more pixels in a sub scanning direction;
• and
• change the input data value of the input multi-value pixel data, into the output data value of the first target reference look-up table to form the output multi-value pixel data, and outputting the output multi-value pixel data for use at the image forming.