Reversible Data Hiding in Image Based on Wavelet Transform 吳祖龍、張世旭
E-mail: [email protected]
ABSTRACT
This paper represents a new approach to reversible data-hiding using discrete wavelet transform in frequency domain.The
continuous set of zero coefficient produced by quantization of the coefficients of the wavelet is used to conceal the data. Most of time, the amount of hidden data and the quality of the image are contradictive. As an advantage, our method can give consideration to both of the two issues. We first transform the cover-image with 3-order wavelet and then do quantization procedure. After doing FDWT & quantization procedures the cover-image were consists of several 64-pixel blocks, and the method presented in this paper is used to insert the secret information into the continuous zero coefficient in the blocks, and then apply wavelet reverse
transformation to compose the stego-image. To extract the secret information, we first calculate the quantized wavelet transform coefficients from the stego-image. Compose each 64-pixel block by combining and permuting due to the extraction method, then using the extraction rules of the combination and permutation of each block to recover the secret information. Besides, the
experiments of alternatively using Haar function for discrete wavelet transform and using 9/7 convolution discrete wavelet transform prove that our method offers expectable and acceptable quality and reversibility of the stego-image. The experiments use a general gray-level image as the cover-image and hide the randomly produced secret bits into this gray-level image, and the evaluation is done by calculating and comparing the amount of hidden data and the quality of the stego-image. Our method is improved from the method of Chang et al. in 2007 and the results of PSNR value and the amount of hidden data are 1.1 times higher than that of the results of Chang et al., respectively. The experiments show that not only the amount of the hidden data but also the quality of the stego-image are both improved in our method.
Keywords : descrete wavelet transformation ; reversible data hiding ; stego-image ; cover-image Table of Contents
目錄 封面內頁 簽名頁 授權書 iii 中文摘要 iv 英文摘要 vi 誌謝 viii 目錄 ix 圖目錄 xi 表目錄 xiii 第一章 緒論 1 1.1 前言 1 1.2 研究背景 2 1.3 研究目的 4 1.4 論文架構 5 第二章 相關研究 6 2.1 相關文獻研究 6 2.2 小波轉換 7 2.2.1 Haar的函數的離散小 波轉換 8 2.2.2旋積分式小波轉換 11 2.3 小波量化 15 第三章 基於小波轉換的可逆資料隱藏方法 18 3.1 嵌入及萃取流程 18 3.2 區塊組成及排列 18 3.2.1 四元樹（Quadtree）的觀念 18 3.2.2 區塊（block）的組成及排列 19 3.3 秘密資訊的隱藏 21 3.3.1 嵌入程序 21 3.3.2 混淆情況的排除 23 3.3.3 嵌入的例子 23 3.3.4 淬取及回復程序 24 第四章 實驗結果 27 4.1 相關環境 27 4.2實驗架構 28 4.3實驗結果 29 第五章 結論與未來研究方向 42 參考文獻 43 圖目錄 圖1 Chang[11]的隱藏資訊流程圖 6 圖2 嵌入組序 （set for embedding） 7 圖3 Haar函數的離散小波轉換流程圖 9 圖4 第一步驟水平切割 10 圖5 第二步驟垂直切 割 11 圖6 橫向小波轉換 13 圖7 鏡射法小波轉換的資料結構 14 圖8 縱向小波轉換 15 圖9 資料隱藏流程圖 18 圖10 資料萃取 流程圖 18 圖11 （a）三階小波轉換 19 圖11 （b）各頻帶小波係數四元樹關係圖 19 圖12 原圖經三階小波轉換後產生的頻帶 及組成區塊的係數關係圖 20 圖13 Block係數的排列示意圖 21 圖14 小波量化後係數示意圖 22 圖15 造成混淆的嵌入組示意 圖 22 圖16 以8×8區塊為例的嵌入範例（a）原始係數區塊 24 圖16 （b）混淆情況修改後的係數區塊 24 圖16 （c）隱藏後 的結果 24 圖17 回復範例（a）隱藏後的結果 26 圖17 （b）回復隱藏係數為0 26 圖17 （c）混淆情況組係數的回復 26 圖18 實驗中所使用的原始影像 28 圖19 實驗流程示意圖 29 圖20 六張利用Haar小波轉換及量化在L=12資料隱藏量的偽裝影像 34 圖21 六張利用9/7小波轉換及量化在L=12資料隱藏量的偽裝影像 36 圖22 六張利用Haar小波轉換及量化在L=12資料隱藏量 的偽裝影像 38 圖23 六張利用9/7小波轉換及量化在L=12資料隱藏量的偽裝影像 40 表目錄 表1 Daubechies 的「9/7」濾波 器係數 12 表2 六張以DCT標準量化表量化的cover-image的PSNR1做調整的 9/7 小波量化係數 16 表3 六張以DCT標準量化 表量化的cover-image的PSNR1做調整的 Haar 小波量化係數 16 表4 六張以DCT修改的量化表量化的cover-image的PSNR1做 調整的 9/7 小波量化係數 17 表5 六張以DCT修改的量化表量化的cover-image的PSNR1做調整的 Haar 小波量化係數 17 表6 比較在DCT的標準量化表之下相同PSNR1量化的cover-image的最大資料藏入量 31 表7 相對於表1,的最大藏入量時
的stego-image的影像品質 31 表8 比較在DCT的修改量化表之下相同PSNR1量化的cover-image的最大資料藏入量 32 表9 相 對於表3,的最大藏入量時的stego-image的影像品質 32 表10 在PSNR1同DCT standard quantization table 之下Haar wavelet 資 料藏入量 33 表11 在PSNR1同DCT standard quantization table 之下Haar wavelet stego-image的影像品質 34 表12 在PSNR1 同DCT standard quantization table 之下9/7 wavelet資料藏入量 35 表13 在PSNR1同DCT standard quantization table 之下9/7 wavelet stego-image的影像品質 36 表14 在PSNR1同DCT modified quantization table 之下Haar wavelet 資料藏入量 37 表15
在PSNR1同DCT modified quantization table 之下Haar wavelet stego-image的影像品質 38 表16 在PSNR1同DCT Modified quantization table 之下9/7 wavelet資料藏入量 39 表17 在PSNR1同DCT modified quantization table 之下9/7 wavelet stego-image的影像品質 39
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