An Adaptive Method for Image Recovery in the DFT Domain

In image authentication research, a common approach is to divide a given image into a number of smaller blocks, and embed a fragile watermark into each block. The modifications can therefore be detected in the blocks that have been tampered with. The literature includes many authentication techniques for detecting modifications only. In this paper, we propose a method for recovering the damaged blocks using the magnitudes of DFT coefficients. If a given block is considered to be damaged, we divide it into 2x2 blocks, and replace the magnitude of the DFT coefficient F(0,0) with the predicted magnitude close to the original image. As the F(0,0) coefficients are always real, we quantize them and round them off. An index map and a small set of DFT coefficients from the original image are employed for image recovery and are sent from the sender to the receiver using a public key scheme. As an image authentication system, we will use the scheme proposed by Wong and Memon. In our experiments, the results demonstrate that the efficacy of the proposed algorithm is good in locally uniform regions and on edges and textures.