1. An image processing method, comprising: acquiring an original image to be processed; acquiring original information to be embedded; generating overlay information including the original information; determining a position in the original image to embed a bit of the overlay information; evaluating whether the overlay information is embeddable in the original image; and controlling image processing so as to select an image processing operation according to a result of the evaluation, wherein the controlling superimposes the overlay information on the original image to generate a superimposed image and outputs the superimposed image onto a sheet when the evaluating judges that the overlay information is embeddable, and the controlling outputs an alert message for notifying that the original information has not been embedded and no image is to be output when the evaluating judges that the overlay information is not embeddable.