It will hash all SIFT features keypoint of all fingerprint images then build the hash table for lookup.

相似图片搜索.关键技术："感知哈希算法"（Perceptual hash algorithm），它的作用是对每张图片生成一个"指纹"（fingerprint）字符串，然后比较不同图片的指纹。结果越接近，就说明图片越相似。 -Similar image search. Key technologies: perception of the hash algorithm (the Perceptual hash algorithm), it is the role of each image t