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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/35753

    Title: 多目的半色調影像浮水印技術之研究
    Other Titles: A study of multi-purpose halftone image watermarking
    Authors: 葉冠廷;Yeh, Kuan-ting
    Contributors: 淡江大學電機工程學系碩士班
    謝景棠;Hsieh, Ching-tang
    Keywords: 半色調影像;Zernike動量;點陣調色法;Halftone Image;Zernike Moment;Ordered Dithering
    Date: 2006
    Issue Date: 2010-01-11 07:06:34 (UTC+8)
    Abstract: 在許多印刷出版的應用方面,我們會希望在半色調的影像中嵌入某些資料來達到版權的控制或是認證的目的,不管如何,在半色調影像浮水印的技術中,抵抗幾何攻擊仍然是主要的問題。

    在本篇論文中,提出一個多目的彩色半色調與半色調數位影像浮水印利用Dithering的技術基於小波轉換與Zernike Moment;對於彩色影像,將彩色影像分解成RGB 三層,利用彩色模型的特性,我們選擇G層來嵌入我們的強健性浮水印,B層用來嵌入我們的易碎浮水印,使用兩個產生不同紋理的臨界值矩陣來作為嵌入強健性浮水印的依據,而使用兩個產生類似紋理的臨界值矩陣來作為嵌入易碎浮水印的依據,Zernike Moment用來偵測嵌入浮水印後的影像所旋轉的角度或縮放的倍率;實驗的結果證明了使用Dithering的技術讓彩色半色調影像能有不錯的影像品質,強健性浮水印能夠抵抗各種的攻擊,像是剪裁、塗鴉、旋轉、縮放等,而易碎浮水印能夠顯示出被剪裁或塗鴉過的區域。

    對於灰階影像,將灰階影像轉成半色調影像的過程中利用兩個產生不同紋理臨界值矩陣嵌入我們的強健性浮水印,再利用兩個與原本臨界值矩陣相近的臨界值矩陣來作為影像是否被攻擊過的依據,強健性浮水印能夠抵抗各種的攻擊,像是剪裁、塗鴉、旋轉、縮放等,更可以抵抗Print & Scan 的攻擊,其Correct DR值仍可超過0.75,而易碎浮水印不需再對影像做任何的修改,不但可以保有原本影像的品質,亦能夠顯示出被剪裁或塗鴉過的區域。

    利用Zernike Moment來偵測影像旋轉的角度與縮放的倍率,必須要求影像的完整性,一但影像受到破壞再旋轉或是旋轉之後受到破壞,Zernike Moment則無法計算出影像旋轉的角度,無法抵抗雙重攻擊。因此,本文提出以影像的中心為圓心,以固定的半徑往外延伸,計算每一個甜甜圈的Zernike Moment值;再利用排序法,選出間距較小的角度,則可計算出影像所旋轉的角度,即使旋轉後某些部分受到破壞或受到破壞後再旋轉,仍可利用沒有遭受破壞的Zernike Moment值,來求得影像旋轉的角度,進而抵抗雙重攻擊。
    In many printer and publishing applications, it is desirable to embed data in halftone images for copyright control and authentication purposes. However, the robustness of the geometrical attacks in halftone watermarking is still a key problem.

    In this paper, we proposed a multipurpose color halftone and halftone watermarking using embedding watermark into the pixel with complicated texture by wavelet transform based on the dithering technique in the halftone processing. For the color image. According to properties of the color model [R,G,B], we chosen the G level for embedded our robust watermark and B level for embedded our semi-fragile watermark. The Zernike moment is adopted to detect rotation and scale of the watermarked image. Experimental results show that watermarked image with good visual quality and the robust watermark is robust to the malicious attacks such as compress, corrupting, cropping, rotating, and scaling. The semi-fragile watermark can detect the regions where attacked by corrupted and cropped.

    For gray-level image, the robust watermark is embedded by using two dither cells which produced different patterns during the halftone processing. We can find out the attacked regions of the image by using two new dither cells which are similar to the original dither cells. Robust watermark is robust to the malicious attacks such as corrupting, cropping, rotating, and scaling. The Correct DR value can close to 0.75 after the attack of print&scan. The semi-fragile watermark can detect the attacked regions and doesn’t need to modify the image. The advantage is to maintain the quality of the halftone image.
    Appears in Collections:[電機工程學系暨研究所] 學位論文

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