Image forming apparatus, image forming method, and image forming program product

An image forming method comprising:

• an image forming step of 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;
• a status conversion step of 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;
• a first reference look-up table determining step of determining a target reference look-up table from among plural reference look-up tables 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 status conversion step from the input multi-value pixel data, and comprise the target pixel and a predetermined number of the adjacent pixels provided on both sides of the target pixel;
• and
• an output data generating step of changing the input data value of the input multi-value pixel data, into the output data value of the target reference look-up table determined at the first reference look-up table determining step 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 perform the steps of:

• an image forming step of 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;
• a status conversion step of 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;
• a first reference look-up table determining step of determining a target reference look-up table from among plural reference look-up tables 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 status conversion step from the input multi-value pixel data, and comprise the target pixel and a predetermined number of the adjacent pixels provided on both sides of the target pixel;
• and
• an output data generating step of changing the input data value of the input multi-value pixel data, into the output data value of the target reference look-up table determined at the first reference look-up table determining step to form the output multi-value pixel data, and outputting the output multi-value pixel data for use at the image forming step.