近年來隨著網路技術的進步，使得各種多媒體資料能夠輕易地在網際網路上傳送，而資訊隱藏技術在此方面亦有著相當的進展。鑑於新一代的影像壓縮技術JPEG2000已漸漸取代以往常用的JPEG壓縮，並擁有更佳的影像壓縮率與品質。因此如何利用JPEG2000所特具之分層編碼及漸進式傳輸(Progressive Transmission)等特點，達到在使用者需求之傳送影像的品質下作資料隱藏是一個值得研究之問題。

　　目前應用於JPEG2000的資料隱藏技術，大部分都針對在量化後小波係數或是區塊最佳壓縮編碼(Embedded Block Coding with Optimized Truncation, EBCOT)之後的分層來藏入資訊。但因隱藏在量化後之小波係數中會因為在EBCOT之過程中為了達到壓縮位元率，有可能會把較不重要的係數刪掉而造成資料的流失，所以利用EBCOT在編碼的過程中會依照影像資料的重要性來重新分配資料所在的位置，將越重要的資料分配到越前面的分層裡的特性將資料嵌入在適當的分層裡，在確保影像品質之條件下達到資料隱藏的目的，將是一種較好的選擇。

　　本論文針對JPEG2000具有之分層編碼與漸進式傳輸之模式，提出一種能對JPEG2000之影像具品質保証之資料隱藏法，此方法在預先設定之資料隱藏控制資訊之控制下，可使用順向或反向之方式來藏入資料，在既定之影像壓縮位元率下，能依照使用者對影像品質的要求來藏入適當之資料量。而解碼端的使用者則能在解壓縮時取得既定品質之影像及隱藏之資料。此一具品質保証之資料隱藏法，經實驗後可以發現比一般的資料隱藏解碼出來的影像品質來的好，且在低位元率與高資料量時則越為明顯。

　With the progress of network techniques in recent years, various multimedia data can be conveyed on internet easily, and information hiding technique also have great improvement in this respect. JPEG, which the most commonly used, has been replaced by JPEG2000 gradually due to its better image quality at low bit rate. Therefore, it is worth to research how to use layer coding and progressive transmission in JPEG2000 to hide data and achieve user demanded quality.

　Most data hiding techniques in JPEG2000 embedded data in quantized DWT coefficients or layers after EBCOT stage. However, in order to reach the targeted bit-rate, insignificant coefficients will be discarded at EBCOT stage result in hided data loss. Because layer coding will reassign image data according to importance at EBCOT. It will be better to hide data in suitable layer to avoid image distortion.

　In this paper, a quality guaranteed data hiding method for JPEG2000 images is proposed. We embedded data in appropriate layer by forward or backward direction based on control information under a fixed compression ratio and user demanded quality. At decode stage, we can also receive demanded quality image and previous hided data.

　Experimental results show that our proposed method preserves better image quality than conventional methods, especially at low bit-rate and high data hiding capacity.

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