Patent ID: 8121414

Claim:
An image processing method for identifying, from a binary image, a plurality of pixel regions where pixels determined to be having the same pixel values are adjacent to each other, extracting, based on a pixel coordinate value of the identified pixel region, a feature point of the pixel region, calculating features of an image based on the extracted feature point, and determining similarity among images based on the calculated features, the method comprising steps of: counting the number of the pixels in the identified pixel region; determining whether the number of the pixels in the identified pixel region is equal to or higher than a first threshold value; extracting the feature point of the pixel region and counting the number of the feature points when the number of the pixels in the identified pixel region has been determined to be equal to or higher than the first threshold value; determining whether the counted number of the feature points is equal to or lower than a second threshold value; calculating the features based on the feature point extracted from the pixel region when the counted number of the feature points has been determined to be above the second threshold value; and changing the first threshold value when the counted number of the feature points has been determined to be equal to or lower than the second threshold value.