Patent ID: 8319863

Claim:
A characteristic value generating circuit having: an acquirer configured to acquire reference data; a generator configured to refer to the reference data and configured to generate a characteristic value of a limit of correction possibility for input image data; and an adder that adds the characteristic value generated by the generator and the input image data, wherein the reference data includes image data obtained by executing predetermined processing for the input image data, wherein the generator comprises a coordinate setter configured to set a coordinate of a center of shading of the image data obtained by executing the predetermined processing, and a weighting processor configured to execute weighting processing dependent on distance from the coordinate set by the coordinate setter, an extractor configured to extract a gap amount between a signal level of the input image data and a signal level of the image data obtained by executing the predetermined processing, and an operation unit configured to multiply a result of weighting processing by the weighting processor by a ratio of the gap amount by the extractor.