sift的C++版，在sift上找出鲁棒性最强的几个特征点，然后以这个点为圆心，以自适应性的尺度为半径画圆，这个非常适合运用于数字水印领域，适用于抵抗数字水印的几何攻击-sift the C++ version, sift out on several features of the robustness of the strongest point, then this point as the center, the scale of self-adaptive radius circle,

The number of changing pixel rate (NPCR) and the unified averaged changed intensity (UACI) are two most common quantities used to uate the strength of image encryption algorithms/ciphers with respect to differential attacks. Conventionall