1. A backlight image determining apparatus comprising: a histogram data generation section that, based on data of pixels constituting an image to be determined, generates data of histograms for respective colors, the histograms representing a distribution of the number of pixels in respect to density values of the respective colors of those pixels; an attribute information obtaining section that obtains, for each color, attribute information relating to a first small region and a second small region by partitioning regions given by the histograms for the respective colors into at least three small regions according to the magnitude of the density values, based on the data of the histograms for the respective colors generated by the histogram data generation section, selecting for each color at least one small region from the at least three small regions as the first small region, and selecting, from the at least three small regions, for each color at least one small region whose density values are larger than those of the first small region and which is not adjacent to the first small region, as the second small region; and a determination section that determines whether the image to be determined is a backlight image, based on the attribute information relating to the first small region for each color and the attribute information relating to the second small region for each color, which is obtained with the attribute information obtaining section.