A reduced-image creating portion creates a reduced image from an original image. A reduced-retinex-image forming portion calculates reflectance of each pixel in the reduced image, thereby forming a reduced retinex image. A normalizing-parameter setting portion obtains frequencies of the reflectance in the reduced retinex image and sets upper and lower limits for normalization. A first normalizing portion obtains a normalized reflectance for each pixel in the reduced image. A first correcting portion obtains a corrected reduced image. A preview-image displaying portion displays the corrected reduced image on a display unit. A retinex-image forming portion calculates reflectance of each pixel in the original image. A second normalizing portion normalizes the reflectance of the original image based on the upper limit and the lower limit, thereby obtaining a normalized reflectance for each pixel in the original image. A second correcting portion corrects the original image, thereby obtaining a corrected original image.