A provisional coefficient acquirer of an image processing apparatus acquires provisional coefficients for projection conversion of an image, on the basis of feature points indicating features of the image. A polygon converter does projection conversion on a polygon having a plurality of fixed points as vertices, on the basis of the provisional coefficients acquired by the provisional coefficient acquirer. A transformation degree acquirer acquires a transformation degree indicating a magnitude of the transformation degree of the polygon from the pre-projection-conversion polygon and the post-projection-conversion polygon. A determiner determines whether the transformation degree acquired by the transformation degree acquirer exceeds a permitted transformation degree. When the determiner determines that the transformation degree does not exceed the permitted transformation degree, a projection converter does projection conversion on the image using as actual coefficients the provisional coefficients acquired by the provisional coefficient acquirer.