植基於伽瑪校正的廣泛半可見可視性浮水印技術

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Please use this identifier to cite or link to this item: http://140.128.103.80:8080/handle/310901/605

Title:	植基於伽瑪校正的廣泛半可見可視性浮水印技術
Other Titles:	A Comprehensive Unseen Visible Watermarking Scheme Based on Gamma Correction
Authors:	鍾蓉蓉 Chung, Jung-Jung
Contributors:	劉榮春;林祝興 Liu, Jung-Chun;Lin, Chu-Hsing 東海大學資訊工程學系
Keywords:	二元影像;飽和度;HSV模型;伽瑪校正;資料隱藏 Binary images;Gamma Correction;Saturation;HSV model;Data hiding
Date:	2010
Issue Date:	2011-01-05T08:40:53Z (UTC)
Abstract:	隨著數位時代的來臨，越來越多的檔案是透過數位化方式儲存，這種方法更是方便與快速。數位化的儲存方式儼然已成為趨勢，但要如何證明此份文件的所有權已成為重要的研究議題。在本論文中，我們提出有別於一般的數位浮水印技術，它擁有可視性浮水印與不可視性浮水印的特性。我們所提出的方法，於一般的情況下，用來傳遞多媒體數位內容的詮釋資料 (Metadata) 或浮水印經由伽瑪校正 (Gamma Correction) 或飽和度的調整，便可將隱藏的浮水印顯示出來。提出的方法有個顯著的特點，嵌入浮水印後的圖 (Stego-images) 與原始圖片 (Cover image) 差異不大，人眼難以察覺，但調動可視角度後，即可顯示隱藏的浮水印。我們嵌入半可見可視性的浮水印於原始圖片是調整模型中的飽和度 (Saturation)。HSV 模型是用來表示 RGB 色彩模型中的圓柱座標點。利用被嵌入範圍與週遭像素值的變化，可將浮水印顯示出來。被嵌入的浮水印可隨著圖片背景的顏色而去改變，不再只是單純的二元影像，所以擁有極高的隱藏效果。而且可以依照嵌入範圍內 R, G和B 的比例調整其浮水印的強度可保留原有的可視品質。由實驗結果得知， Stego-images 的PSNR值可超過 40 dB，甚至高達 50 dB。 With the advent of the digital era, lots of files are stored in digital formats for quick and easy access. Documents stored as digital format have become the trend, and how to effectively prove the ownership of the digital document has developed into an important research issue. In this thesis, we propose a novel watermark scheme with unique features that consist of useful properties from the visible watermarking and invisible watermarking schemes. In this work, originally invisible patterns carrying metadata, or the watermark, can be revealed by the gamma correction method or by adjustment of saturation of the stego-image. One salient characteristic of the proposed watermark scheme is that we can obtain a stego-image similar to the cover image that is hard to tell them apart by the naked eye, however the unseen embedded watermarks can be revealed by adjusting the viewing angle. We embed unseen visible watermarks in the cover image by adjusting saturation values in the HSV model, a common cylindrical-coordinate representation of points in the RGB color model. The embedded watermark is revealed in the place where significant variances are found among neighboring pixels. Instead of mere binary image, the embedded watermark adapts its color according to the background color of the original cover image to have a better hidden effect. Also, based on ratios of R, G, and B values, we can adaptively adjust the strength of the watermark to retain the visual quality of the stego-image. As demonstrated by the experimental results, the PSNR values of the stego-image are more than 40 dB, sometimes even as high as 50 dB.
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