pHash is an implementation of various perceptual hashing algorithms. A perceptual hash is a fingerprint of an audio, video, or image file that is mathematically based on the audio or visual content contained within. Unlike cryptographic hash function

矩阵的简单计算，包括加，减，乘，除。实现矩阵的代码操作-The algorithm has several optional matrices, and the image can be restored through reverse transform. Thus, it is very difficult to decode the hashing algorithm