1. An image processing method for correcting an original image, the method comprising: performing a retinex processing on a luminance signal of each pixel in an original image that is indicative of a luminance component of an original color of each pixel; determining, for each pixel, a retinex-processed pixel value based on the luminance signal that has been subjected to the retinex processing and at least one signal other than the luminance signal that is indicative of a component other than the luminance component of the original color of the each pixel; generating a histogram by counting a rate of occurrence of the retinex-processed pixel values for each level over a predetermined first range of pixel values to which the retinex-processed pixel value is possibly assigned; and reassigning each pixel value based on the histogram.