1. An image processing apparatus comprising: storage means in which regression coefficient data is stored for each class on the basis of a tap in which a linear feature amount corresponding to a pixel of interest of first image data of an input first image and a non-linear feature amount determined from the first image data of the input first image are used as elements; classification means for classifying each of linear feature amounts of a plurality of items of the first image data of the input first image into a predetermined class; reading means for reading, from the storage means, the regression coefficient data corresponding to the class determined by the classification means; and data generation means for generating data of a second image obtained by making the input first image have higher quality by performing a product-sum computation process by using the regression coefficient data read from the reading means and elements of the tap of each of the plurality of items of the first image data of the input first image.