1. An image processing apparatus comprising: distorted circular image storing unit that stores a pixel information group configuring a distorted circular image generated based on the externally-input distorted circular image photographed by a wide-angle lens or omnidirectional mirror; converting unit that converts the stored pixel information group configuring the distorted circular image into a pixel information group configuring a 2D-viewable planar regular image; planar regular image storing unit that stores the pixel information group configuring the converted planar regular image; selection-instruction receiving unit that receives an instruction of selecting pixel information corresponding to an arbitrary point on the stored planar regular image; corresponding coordinate specifying unit that specifies pixel information on a distorted circular image corresponding to the pixel information on the selection-instructed planar regular image; and reconverting unit that reconverts the stored pixel information group configuring the distorted circular image into a pixel information group configuring a 2D-viewable planar regular image about the specified pixel information.