Image forming apparatus

An image forming apparatus comprising:

• a plurality of head units provided for each of colors for forming a color image, and each including an ink head that ejects ink, thereby forming an image on a recording sheet;
• a plurality of drive devices that each drive a corresponding one of the plurality of ink heads that eject the ink of a same color, and cause the ink head to eject the ink;
• an output tray that receives the recording sheet on which the image has been formed by the ink heads;
• a document reading device that reads an image of a document;
• a control device comprising a processor and functioning, through the processor executing a control program, as a controller that causes the plurality of ink heads, by controlling the drive device on a basis of a predetermined reference voltage, to eject the ink thereby forming a test chart composed of a predetermined pattern of images, on the recording sheet, and delivers the recording sheet on which the test chart has been formed, to the output tray;
• a density calculator that analyzes the images of the test chart, acquired by the document reading device through reading of the recording sheet on which the test chart has been formed, and calculates density of the images, respectively formed by the plurality of ink heads, with respect to each of the images;
• a decider that decides whether the density of each of the images respectively formed by the plurality of ink heads is within a range defined by a predetermined threshold, from a density average of the images respectively formed by the plurality of ink heads of the same color;
• and
• an adjustment value calculator that calculates, with respect to the ink head that has formed the image, the density of which has been decided by the decider to be deviated from the predetermined range, an adjustment value for adjusting the reference voltage to be used by the drive device driving the ink head, such that the density of the image to be formed becomes closer to the density average.