Image forming apparatus, method for deriving correction data, and non-transitory computer-readable storage medium

An image forming apparatus includes an image forming device, a reading device, and circuitry. The image forming device discharges ink droplets through nozzles to form an image on a recording medium conveyed in a first direction. The reading device reads the image formed on the recording medium. The circuitry generates a correction chart that includes patches, located in the first direction and representing different densities from each other, and two marks located at different positions from each other in a second direction perpendicular to the first direction. The circuitry locates opposed end portions of the patches in the second direction outside the two marks in the second direction. The circuitry derives correction data, based on read data of an area of the patches existing inside the two marks in the second direction included in read data provided by the reading device reading the correction chart formed on the recording medium.