1. An image processing device comprising: a focal pixel setting unit that is configured to set a focal pixel among a plurality of pixels in an original image that is represented by original image data; a near pixel setting unit that is configured to set a pixel near the focal pixel as a near pixel; a calculating unit that is configured to calculate a characteristic value related to luminance of the focal pixel and luminance of the near pixel; a target pixel determining unit that is configured to determine, as the target pixel, the focal pixel whose characteristic value satisfies a prescribed condition; and an editing unit that is configured to generate edited image data by editing the original image data, the edited image data representing an edited image having a supplemental image superimposed on the original image, the supplemental image being superimposed on an area encompassing the target pixel.