1. An image processing apparatus comprising: a display control section that controls a projection device that projects an image on a projection surface to project a correction image; a captured image data acquisition section that acquires captured image data obtained by capturing the correction image projected by the projection device; a judgment section that judges, when the correction image expressed by the captured image data acquired by the captured image data acquisition section is placed in a plane with a coordinate system, which of the following functions: a function representing a straight line; and a function representing a curved line is used to make image correction based on the distance between the correction image and at least one of a line expressed by the function representing a straight line and a line expressed by the function representing a curved line; and a presentation section that presents a user with an operation screen for correction using the function judged by the judgment section to be used for the image correction.