1. An image processing method, comprising: a setting step of setting interpolation filter coefficients which are used in an interpolation calculation and generated from a high-frequency/high-quality image which is generated by extracting a high-frequency component of a high-quality image, and a high-frequency/low-quality image which is generated by extracting a high-frequency component of a low-quality image, the high-quality image and the low-quality image being in a pair having image qualities different from each other, as well as from a representative high-frequency image corresponding to any of a previously set number of classes into which the high-frequency/low-quality image is converted as representative values, and setting the representative high-frequency image; a high-frequency/low-quality image generation step of generating a high-frequency/low-quality image by extracting a high-frequency component of a low-quality image which is an input image in a restoration processing; and a high-quality-image generation step of generating a super-high-frequency component which does not exist in the high-frequency/low-quality image by applying an interpolation calculation process using the set interpolation filter coefficients and the set representative high-frequency image to each pixel of the generated high-frequency/low-quality image, and including the generated super-high-frequency component into the low-quality image to generate a high quality image which has an image quality higher than the low-quality image.