Image forming apparatus, image forming method, and image forming program storage medium

A set value output circuit includes a first output unit and a second output unit. The first output unit outputs a signal input to a first input when a first timing signal is input to a second input, and continues to output the signal until a next first timing signal is input. The second output unit outputs the signal input to a third input when the second timing signal is input to a fourth input, and continues to output the signal until a next second timing signal is input. A selection unit inputs a selected timing signal as the second timing signal to the fourth input. A control unit inputs the first timing signal to the second input, so that a set value for an image to be formed next is output during image formation using the signal output from the second output.