A study of multi-purpose halftone image watermarking
| Autor: | Kuan-Ting Yeh, 葉冠廷 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 94 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. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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