Integer DCT-based reversible watermarking for images using companding technique

摘要: We present a high capacity reversible watermarking scheme using companding technique over integer DCT coefficients of image blocks. This takes advantage DCT coefficients' Laplacian-shape-like distribution, which permits low distortion between the watermarked and original one caused by bit-shift operations in embedding process. In our scheme, we choose AC coefficients domain for bit-shift operation, therefore the capacity quality can be adjusted selecting different numbers of different frequencies. To prevent overflows underflows spatial modification DCT coefficients, design block discrimination structure to find suitable blocks that used without overflow or underflow problems. also use this embed an overhead location information all embedding. With watermark bits embedded saved LSBs of coefficient blocks, retrieved correctly during extraction, while restored perfectly.