提出通過對分塊圖像的DCT 系數進行動態范圍壓縮來改進傳統的基于DCT 變換的圖像自嵌入水印算法，并結合灰度變換函數與JPEG 標準量化表重新設計了DCT 系數碼長分配表，大幅度提升了量化過程保留的圖像頻段范圍，使水印圖像在遭受篡改攻擊后能較好地恢復；最后，給出了MATLAB 的算法實現。
關鍵詞：DCT；水印；MATLAB；碼長；動態壓縮；自嵌入
Abstract: In this paper, a better scheme of self2embedding an image into itself is proposed by compressing the dynamic range of DCT coefficients , whose bit lengths are nicely chosen according to gray transforming function and standard JPEG quantization table. By this scheme , the image’s frequency segment is largely extended which could be saved, and the watermarking image tampered could be properly recovered . In addition ,the key algorithm,
which comes true in MATLAB, is amply analyzed in this paper.
Key words: DCT ; watermark; MATLAB; code length; dynamic compression; self2embedding