A narrow area artificial image degree calculator 915 calculates a narrow area artificial image degree from the positional relation of the extracted narrow area feature amount for a statistical distribution range in a two-dimensional space of PNDP (primary narrow discrimination parameter) and SNDP (secondary narrow discrimination parameter) as the small area feature amount. 狭域人工画度算出部915は、狭域特徴量であるPNDPおよびSNDPの2次元空間における統計的な分布範囲に対する、抽出された狭域特徴量の位置関係により、狭域人工画度を算出する。 - 特許庁