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    • 1. 发明授权
    • Semi-fragile watermarks
    • 半脆弱水印
    • US06834344B1
    • 2004-12-21
    • US09398203
    • 1999-09-17
    • Gaurav AggarwalPradeep K. DubeyAshutosh KulshreshthaMarco MartensCharles P. TresserChai W. Wu
    • Gaurav AggarwalPradeep K. DubeyAshutosh KulshreshthaMarco MartensCharles P. TresserChai W. Wu
    • H04L900
    • G06T1/005G06T1/0042H04N1/32144H04N1/32154H04N2201/327
    • A method is presented for marking high-quality digital images with a robust and invisible watermark. It requires the mark to survive and remain detectable and authenticatable through all image manipulations that in themselves do not damage the image beyond useability. These manipulations include JPEG “lossy” compression and, in the extreme, the printing and rescanning of the image. The watermark also has the property that it can detect if the essential contents of the image has changed. The first phase of the method comprises extracting a digest or number N from the image so that N only (or mostly) depends on the essential information content, such that the same number N can be obtained from a scan of a high quality print of the image, from the compressed form of the image, or in general, from the image after minor modifications (introduced inadvertently by processing, noise etc.). The second phase comprises the marking. This can be done in form of an invisible robust watermark, or in form of some visible signature or watermark.
    • 提出了一种用强大且不可见的水印标记高质量数字图像的方法。 它需要标记生存,并通过所有图像操作保持可检测和可认证,这本身不会损害图像超出可用性。 这些操作包括JPEG“有损”压缩,在极端情况下,打印和重新扫描图像。 该水印还具有可以检测图像的基本内容是否已改变的属性。 该方法的第一阶段包括从图像中提取摘要或数字N,使得仅N(或主要地)取决于基本信息内容,使得可以从扫描的高质量打印获得相同数量N 图像,从图像的压缩形式,或一般来说,从稍后修改的图像(通过处理,噪声等无意中引入)。 第二阶段包括标记。 这可以以不可见的鲁棒水印的形式或以一些可见的签名或水印的形式来完成。
    • 4. 发明授权
    • Compressed image authentication and verification
    • 压缩图像认证和验证
    • US06275599B1
    • 2001-08-14
    • US09143354
    • 1998-08-28
    • Roy L. AdlerBruce P. KitchensCharles P. TresserChai W. Wu
    • Roy L. AdlerBruce P. KitchensCharles P. TresserChai W. Wu
    • G06K900
    • G06T1/0042G06T2201/0052G06T2201/0053
    • A watermarking method involves mostly invisible artifacts and is sensitive to any modification of the picture at the level of precision rendered by the compressed version of the image. The image is compressed according to a known compression standard, such as the JPEG standard, and with a fixed quality setting. Using the JPEG standard, the original image is cut into blocks to which the Discrete Cosine Transform (DCT) is applied and the DCT coefficients quantized. The watermark according to the invention is applied to the quantized DCT coefficients. This is done using an encryption function, such as a secret key/public key algorithm. The JPEG compression is then completed using a lossless compression scheme, such as Huffman coding, to produce the compressed and watermarked image. Authentication of the compressed and watermarked image begins with a lossless decompression scheme to obtain the set of quantized DCT coefficients. The coefficients are authenticated, and the DCT output of each block is dequantized. If necessary, an inverse DCT is applied to each block to output the decompressed watermarked image.
    • 水印方法主要涉及不可见的伪像,并且对图像的压缩版本呈现的精度水平对图像的任何修改都敏感。 图像根据已知的压缩标准(例如JPEG标准)被压缩,并且具有固定的质量设置。 使用JPEG标准,原始图像被切割成应用了离散余弦变换(DCT)并且DCT系数被量化的块。 根据本发明的水印被应用于量化的DCT系数。 这是使用加密功能完成的,例如秘密密钥/公钥算法。 然后使用诸如霍夫曼编码的无损压缩方案完成JPEG压缩,以产生压缩和加水印的图像。 压缩和加水印图像的认证以无损解压缩方案开始,以获得量化的DCT系数集合。 系数被认证,并且每个块的DCT输出被去量化。 如果需要,对每个块应用逆DCT以输出解压缩的水印图像。