Patent ID: 7370929

Claim:
An inkjet printer for printing a halftone image generated by comparing a grayscale original image with a dither matrix, comprising: a head having a plurality of outlets arranged in a width direction perpendicular to a predetermined scan direction each of which ejects droplets of ink onto a printing medium; a scanning mechanism for moving said printing medium relatively to said head in said scan direction; a matrix memory for storing a modified dither matrix which is a two-dimensional array where a plurality of element values are arranged in a column direction corresponding to said scan direction and a row direction corresponding to said width direction, a plurality of positions in said row direction as many as said plurality of outlets are associated with said plurality of outlets, respectively, and said plurality of element values are modified on the basis of variation in print densities with respect to said width direction caused by ejection from said plurality of outlets; and an ejection controller for controlling ejection of ink from said plurality of outlets, in accordance with comparison results between pixel values of said original image at positions of said plurality of outlets relative to said printing medium and element values of said modified dither matrix corresponding to said pixel values, in synchronization with movement of said printing medium relative to said head.