一种频域加密算法，图像经过DCT变换得到DCT系数，然后对DCT系数进行加密。然后对加密的DCT系数进行DCT反变换图像数据。最后对其加密后的图像数据进行线性变换来调整图像数据的取值范围在[0，255]。最后得到加密图像-A frequency-domain encryption algorithm, the image obtained through the DCT transform DCT coefficients, and then encrypt the DCT coefficients. And then encrypted DCT coefficients DCT inverse transform image data. The last of its encrypted image data linear transformation to adjust the image data ranges in [0,255]. Finally the image is encrypted