Image forming apparatus and flushing control method for assigning respective dot patterns for use in flushing with inks of different colors according to number of overlapping dots in image

An image forming apparatus comprising:

• a recording head that ejects inks of a plurality of different colors on a recording medium to form an image based on image data;
• a storage device that stores a plurality of different dot patterns for flushing;
• and
• a control device that includes a processor and functions, through the processor operating in accordance with a control program, as:
• a controller that allows the recording head to execute flushing which is forcible ejection of the inks;
• an image area detector that detects an image area in the image data;
• an overlapping dot counter that counts a number of dots overlapping with the image area for each of the plurality of different dot patterns if an ink is to be forcibly ejected on the image area under control of the controller according to the each of the plurality of different dot patterns;
• and
• a dot pattern assignor that assigns, according to the number of overlapping dots, each of the plurality of different dot patterns for use in flushing with each of the inks of the plurality of different colors.