Patent ID: 7484822

Claim:
An image forming method for forming an image on a recording medium by forming dots on the recording medium by depositing droplets on the recording medium by a recording head having a plurality of nozzles ejecting the droplets while moving the recording head and the recording medium relatively to each other by conveying at least one of the recording head and the recording medium in a relative conveyance direction, wherein the image to be formed is divided into a plurality of regions; a density in each of the plurality of regions is set as a prescribed density so as to form the image; a droplet deposition rate is defined as a ratio of a number of the dots actually formed by depositing the droplets from one of the nozzles within each of the plurality of regions with respect to a maximum number of the dots formable by depositing the droplets from the one of the nozzles within the region; and tonal gradation in the image is represented by means of a collection of the dots based on a dot arrangement specified according to the droplet deposition rate calculated from image data of the image to be formed, the image forming method comprising: a droplet deposition rate calculation step of calculating the droplet deposition rate from the image data; a dot arrangement specification step of specifying a dot arrangement pattern from the droplet deposition rate calculated in the droplet deposition rate calculation step; and a droplet deposition control step of controlling droplet deposition operation performed by the recording head in such a manner that the dot arrangement pattern specified in the dot arrangement specification step is achieved, wherein, in at least one of the plurality of the regions where the droplet deposition rate calculated in the droplet deposition rate calculation step is lower than a prescribed reference value, groups of the dots are formed in each of which m dots (where m is a positive integer) are aligned so as to mutually overlap by a prescribed overlap ratio in a main scanning direction substantially perpendicular to the relative conveyance direction, in accordance with the droplet deposition rate calculated in the droplet deposition rate calculation step, and a bent dot line is formed by arranging the groups of the dots, each including m dots, in the main scanning direction while staggering the groups of the dots in the sub-scanning direction, wherein the image is completed by a consistent movement in a single direction, between the recording head and the recording medium.