1. An image processing device comprising: a normal-light-image storage unit that stores therein each picture signal of a normal light image of an observed region, the normal light image being captured by a normal-light imaging unit that receives normal light from the observed region via a plurality of color filters having different spectral characteristics; a fluorescence-image storage unit that stores therein each picture signal of a fluorescence image of the observed region, the fluorescence image being captured by a fluorescence imaging unit that receives fluorescence generated from the observed region irradiated with excitation light; a uniform-image generating unit that extracts each picture signal corresponding to a specific color filter, which is one of the plurality of color filters and transmits light in a wavelength band for which a light absorption property of a contrast region in the observed region is low, from among each picture signal of the normal light image stored in the normal-light-image storage unit, and generates a uniform image of a wavelength-band component corresponding to the specific color filter based on each extracted picture signal; and a correction processing unit that corrects each picture signal of the fluorescence image stored in the fluorescence-image storage unit by using the uniform image; wherein the plurality of color filters include a plurality of red light filters that transmit red light, a plurality of green filters that transmit green light, and a plurality of blue filters that transmit blue light, and the red light filters among the plurality of color filters serve as the specific color filter; and wherein: the uniform-image generating unit includes: a signal extracting unit that extracts each picture signal corresponding to the red light filter from among each picture signal of the normal light image stored in the normal-light-image storage unit; and an interpolation processing unit that performs an interpolation process of each picture signal extracted by the signal extracting unit to generate the uniform image of a wavelength-band component corresponding to the red light filter.