1. An image processing device comprising: inputting means for inputting an image; detecting means for detecting a face region in the input image; histogram generating means for generating a first histogram of the entire input image and a second histogram of the detected face region; calculating means for calculating a highlight point and a shadow point of the input image from the first histogram of the entire input image; first generating means for generating a gradation correction for luminance and a gradation correction for each of a plurality of color components based on the highlight point, the shadow point, a target highlight point and a target shadow point; conversion means for converting the second histogram based on the gradation correction generated for the luminance; determining means for determining a representative luminance of the detected face region based on the converted second histogram of the detected face region; second generating means for generating an exposure correction based on the representative luminance; and correcting means for correcting the input image based on the gradation correction generated for each of the plurality of color components and the exposure correction.