1. An image processing apparatus for coupling to an imaging apparatus that generates a captured image covering substantially a 360-degree field of view and for transmitting an output image to an image forming apparatus, the image processing apparatus comprising: a memory; and a processor coupled to the memory and configured to perform functions of: a setting unit configured to select a type of a polyhedron that is to be constructed by folding a development printed on a medium according to the output image; a converter configured to perform a conversion process to convert two-dimensional coordinates in the captured image into two-dimensional coordinates in the development that is to be printed on the medium and folded to construct the polyhedron, such that a zenith in the captured image is printed at a topmost point of the polyhedron constructed by folding the development printed on the medium; and an image generator configured to generate the output image based on the converted coordinates, wherein the conversion process includes: calculating conversion between the two-dimensional coordinates in the captured image and three-dimensional coordinates on the polyhedron to be constructed; and calculating conversion between the three-dimensional coordinates on the polyhedron and the two-dimensional coordinates in the development, and wherein the three-dimensional coordinates on the polyhedron vary in response to a placement position of the polyhedron.