數位浮水印之研究

Abstract

近年來因為電腦與網際網路的快速發展與數位資料被大量的使用，經由全球資訊網，許多數位影像能被很容易地傳遞與複製，如此使得智慧財產權的保護成為一個重要的課題。而數位浮水印技術為此問題提供一個解決方案。數位浮水印可以分為可視浮水印與不可視浮水印兩大類。本論文將介紹在彩色或灰階影像上的可視浮水印技術與在彩色影像上的不可視浮水印技術以保護版權。所提出的可視浮水印在空間平面上以修改影像亮度或顏色的方法來加入浮水印，而不可視浮水印則將浮水印藏入影像的藍色層。所藏入的不可視浮水印可以是文字、影像或序號，在藏入或取出浮水印時必須使用同一個密碼，而且此法在取回浮水印時並不需要原圖，並且能有效對抗某些影像處理與JPEG壓縮的破壞。

The development of computers and Internet has exploded in the last few years, and the digital data is used popularly. The digital images are distributed and duplicated easily through WWW, thus the protection of the intellectual property rights of digital images becomes an important issue. The digital watermarking technology provides a good solution for this issue. There are two kinds of digital watermarks: visible and invisible. In this paper, the visible watermarking methods on digital gray-scale or color images and the invisible watermarking methods on digital color images for copyright protection are presented. The visible digital watermarking methods can embed a monochrome or color copyright mark in a digital image and it is performed in the spatial domain through modifying the intensities or color of pixels. The invisible digital watermarking is to hide an invisible signal in the image, and the embedded signal can be an image, a text or a serial number that describes the copyright of the image. The proposed invisible watermarking method modifies the blue channel of the color image to embed the watermark. A secret key is used in the watermark embedding and retrieving processes to enhance the security issue. The retrieval of the invisible watermark does not refer to the original image. In addition, the proposed method is resistant to some image-processing operations and JPEG compression to some degree.