The entire disclosure of Japanese patent Application No. 2019-148530, filed on Aug. 13, 2019, is incorporated herein by reference in its entirety.

BACKGROUND

Technological Field

The present invention relates to an image forming apparatus, an image data adjustment method, and an image data adjustment program.

Description of the Related Art

There have been inkjet image forming apparatuses that eject ink onto a recording medium transported by a transportation device from nozzle orifices of a plurality of aligned nozzles, thereby forming an image on the recording medium. In these inkjet image forming apparatuses, ink ejection failures (also referred to as nozzle missing) can occur, such as clogging of a nozzle or the like decreasing the amount of ink ejection from the nozzle orifice from the initial value and further completely blocking the ejection, or changing the ejection direction.

In the inkjet image forming apparatuses, such ink ejection failures lead to a deterioration in the quality of images formed. Thus, the inkjet image forming apparatuses have regularly inspected the state of ink ejection from nozzle orifices. For the inspection of the ink ejection state, there is a method of capturing a test image formed on a recording medium and analyzing the captured image data. This method has determined an ink ejection failure from each nozzle orifice by causing each nozzle orifice to eject ink individually, and checking the presence or absence of ejection and the density of the ink.

In inkjet recording apparatuses, there are also a complementary technique of adjusting the amount of ink ejection from a nozzle orifice adjacent to a defective nozzle causing an ink ejection failure, based on such an inspection result, thereby compensating for a deterioration in the quality of a formed image caused by the ink ejection failure, and a technique of removing the cause of clogging such as dried ink by cleaning an ink ejection surface.

JP 2017-170862 A describes a technique of taking an out-of-range nozzle that is outside an ejection state allowable range out of use, and adjusting the positions of pixels in image data.

However, the technique described in JP 2017-170862 A has a problem that by adjusting the positions of pixels in image data (especially, rotation or scaling down), an image giving an impression very different from that of an image originally required (expected) by the user is formed on a recording medium, resulting in a deterioration in the quality of the formed image.

SUMMARY

It is an object of the present invention to provide an image forming apparatus, an image data adjustment method, and an image data adjustment program capable of preventing the formation of an image giving an impression very different from that of an image originally required by a user.

To achieve the abovementioned object, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention comprises a hardware processor that: adjusts positions of pixels in image data when an ink ejection failure occurs in a nozzle that forms an image by ejecting ink, so as to reduce an influence of the ink ejection failure when forming an image based on the image data; and adds pixels to an area in the image data where pixels have disappeared due to the adjustment of the hardware processor.

