1. An image processing apparatus comprising: broad-range feature extraction means for extracting broad-range features including a plurality of types of broad-range features from pixels located in a predetermined area in relation to a subject pixel of a first image; broad-range degree-of-artificiality calculation means for calculating, in a multidimensional space represented by the plurality of types of broad-range features included in the broad-range features extracted by the broad-range feature extraction means, from a positional relationship of the plurality of types of broad-range features according to a statistical distribution range of an artificial image, which exhibits a small number of grayscale levels and distinct edges, of the first image, a broad-range degree of artificiality representing a degree by which the plurality of types of broad-range features belong to the statistical distribution range of the artificial image; narrow-range feature extraction means for extracting narrow-range features including a plurality of types of narrow-range features from pixels located in the predetermined area in relation to the subject pixel of the first image; narrow-range degree-of-artificiality calculation means for calculating, in a multidimensional space represented by the plurality of types of narrow-range features included in the narrow-range features extracted by the narrow-range feature extraction means, from a positional relationship of the plurality of types of narrow-range features according to a statistical distribution range of the artificial image of the first image, a narrow-range degree of artificiality representing a degree by which the plurality of types of narrow-range features belong to the statistical distribution range of the artificial image; and degree-of-artificiality calculation means for calculating a degree of artificiality of the subject pixel by combining the broad-range degree of artificiality and the narrow-range degree of artificiality.