In an image processing apparatus, an image corrector ascertains, for each pixel of a selected pixel region included in an image captured by an imaging unit, luminance-value ratios of respective colors of color filters in accordance with (i) a color luminance value of the corresponding pixel of the selected pixel region, and (ii) ascertainment data items predetermined for the respective colors if a measured illumination level around the imaging unit is lower than or equal to a predetermined threshold illumination level. The ascertainment data item, predetermined for each color, represents a corresponding color luminance-value ratio at any pixel in the selected pixel region with respect to a predetermined peak luminance value of the corresponding color in the selected pixel region. The image corrector generates a corrected image in accordance with the luminance-value ratios of the respective colors ascertained for each pixel of the selected pixel region.