Patent ID: 8107738

Claim:
An image processing method comprising steps of: when an inputted image gets stored as a reference image in a storage section which stores plural kinds of features in association with a plurality of reference images, extracting features from the inputted image; determining whether at least a predetermined number of reference images have already been stored in the storage section in association with an extracted features or not; storing the inputted image in the storage section as a reference image in association with the extracted features when it is determined that a predetermined number of reference images have not been stored; and invalidating the features when it is determined that at least a predetermined number of reference images have already been stored, and then, when a document image is inputted, extracting features from an inputted document image; and judging whether the document image is similar to a reference image or not based on the features extracted from the document image and plural kinds of features which are not invalidated among features stored in the storage section.