1. An image processing device comprising: an image processor operably configured to function as: a reduced image forming unit configured to reduce an original image having original pixels to form a reduced image having reduced pixels, a reduced image size indicated by the number of the reduced pixels being less than an original image size indicated by the number of the original pixels; a first reflectance value calculating unit configured to calculate a first reflectance value for each reduced pixel based on a reduced pixel value of each reduced pixel and an average value of both each reduced pixel value and pixel values of peripheral pixels of each reduced pixel; a normalizing parameter determining unit configured to determine a normalizing parameter based on a distribution of the first reflectance values; a second reflectance value calculating unit configured to calculate a second reflectance value for each original pixel based on an original pixel value of each original pixel and an average value of both each original pixel value and pixel values of peripheral pixels of each original pixel; a normalizing unit configured to normalize the second reflectance values based on the normalizing parameter to obtain normalized Retinex values; a correcting unit configured to correct the original pixel values based on the normalized Retinex values; and a reducing information determining unit configured to determine first information based on second information with respect to at least one of quality of the corrected original image to be formed, a type of a recording medium on which the corrected original image is formed, a size of a recording medium on which the corrected original image is formed, the reduced image size, and the original image size, the reduced image forming unit reducing the original image based on the first information.