1. A computer-readable storage medium having stored therein an image processing program for causing a computer of an image processing apparatus, which is connected to a real camera for capturing an image of a real space and a display device including a screen on which the real space is visible, to act as: real image obtaining means for obtaining a real image showing the real space that is captured by the real camera; color information obtaining means for obtaining color information about at least one pixel of the real image obtained by the real image obtaining means; light source setting means for setting, based on the color information obtained by the color information obtaining means, at least one parameter relating to a color and/or a brightness of a light source placed in a virtual space; object image generation means for generating an object image that is obtained when an image of an object in the virtual space, which object is illuminated by the light source whose at least one parameter has been set by the light source setting means, is captured by the virtual camera; and display control means for causing the display device to display the object image generated by the object image generation means, such that the object image is superimposed on the real space visible on the screen, in a manner to allow a user to view the object image.