1. An image processing apparatus comprising: circuitry configured to: acquire a first plurality of values of a first model parameter by modeling a distribution of pixel values of an input image with a first probability distribution model, the first probability distribution model being a first mixed distribution model including a first plurality of distributions, and the first plurality of values corresponding to peak positions of the first plurality of distributions of the first mixed distribution model, determine control points as references for determining a shape of a tone curve by associating the first plurality of values acquired from the input image to be processed with a second plurality of values of a second model parameter obtained by modeling distribution of pixel values of a reference image with a second probability distribution model in which a type and number of mixtures are same as the first mixed distribution model modeling the pixel values of the input image, the second probability distribution model being a second mixed distribution model including a second plurality of distributions, and the second plurality of values corresponding to peak positions of the second plurality of distributions of the second mixed distribution model, each control point associating the first model parameter of a class with the second model parameter of same class, generate additional control points that associate maximum values and minimum values of a dynamic range of the input image and a dynamic range of the reference image, generate the tone curve based on the determined control points and the generated additional control points, and correct the input image to be processed by using the tone curve.