At least one processor configured as hardware generates gamma correction processing information based on an achromatic color input value and an output value acquired by referencing a three-dimensional LUT based on the achromatic color input value, references the three-dimensional LUT based on a representative input value as a chromatic color input value to acquire a representative output value, sets color difference signal processing information such that the representative output value is obtained when the representative input value is subjected to gamma correction processing and color difference signal processing, and subjects an image signal to gamma correction processing and color difference signal processing.