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公开(公告)号：EP1220152A3
公开(公告)日：2004-11-24
申请号：EP01310111.8
申请日：2001-12-03
IPC分类号： G06T1/00
CPC分类号： G06T1/005 , G06T1/0028 , G06T2201/0052 , G06T2201/0203 , H04N1/32154 , H04N1/3217
摘要： A spatial domain image I produced by a source 1 is combined with watermark data Ri to produce a spatial domain watermarked image I'. The watermarked image is produced by an embedder 3 according to the equationCi'=Ci + α. Ri where Ci and Ci' are wavelet transform coefficients of the image, and α is a scaling factor, α is chosen so that the watermark is imperceptible in the image and to resist removal of the watermark by unauthorised processing. It is desirable that α has the smallest value which achieves that. If α is too big the watermark is perceptible in the image; if it is too small the mark may not survive processing of the image. α is determined from a trial decoding of the image I in a decoder 4. The decoding is that which would be used to decode the watermarked image I'. A value α' is produced by a calculator S3-S8, to which an offset value is added by an adder S9 to produce α. This produces values of α over the image, which are used to scale the data Ri so as to conceal the data. An image is one example of material to which the invention is applicable. The step of producing modified coefficient values C i may not use coefficients of magnitude greater than a threshold T and does not use corresponding information symbols R i . Alternatively, a threshold T clip may be set. The scaling factor α is calculated using clipped coefficient values and coefficients C i of magnitude less than T clip .
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公开(公告)号：EP1220152A2
公开(公告)日：2002-07-03
申请号：EP01310111.8
申请日：2001-12-03
IPC分类号： G06T1/00
CPC分类号： G06T1/005 , G06T1/0028 , G06T2201/0052 , G06T2201/0203 , H04N1/32154 , H04N1/3217
摘要： A spatial domain image I produced by a source 1 is combined with watermark data Ri to produce a spatial domain watermarked image I'. The watermarked image is produced by an embedder 3 according to the equation Ci'=Ci + α. Ri
where Ci and Ci' are wavelet transform coefficients of the image, and α is a scaling factor, α is chosen so that the watermark is imperceptible in the image and to resist removal of the watermark by unauthorised processing. It is desirable that α has the smallest value which achieves that. If α is too big the watermark is perceptible in the image; if it is too small the mark may not survive processing of the image.
α is determined from a trial decoding of the image I in a decoder 4. The decoding is that which would be used to decode the watermarked image I'. A value α' is produced by a calculator S3-S8, to which an offset value is added by an adder S9 to produce α. This produces values of α over the image, which are used to scale the data Ri so as to conceal the data. An image is one example of material to which the invention is applicable.
The step of producing modified coefficient values C i may not use coefficients of magnitude greater than a threshold T and does not use corresponding information symbols R i . Alternatively, a threshold T clip may be set. The scaling factor α is calculated using clipped coefficient values and coefficients C i of magnitude less than T clip .摘要翻译： 由源1产生的空间域图像I与水印数据Ri组合以产生空间域水印图像I'。 水印图像由嵌入器3根据等式
Ci'= Ci +α产生。 其中Ci和Ci'是图像的小波变换系数，α是缩放因子，选择α，使得水印在图像中不可察觉，并且通过未经授权的处理来抵抗水印的去除。 期望α具有实现该值的最小值。 如果alpha太大，则水印在图像中是可感知的; 如果太小，标记可能无法在图像的处理中生存。 从解码器4中的图像I的试用解码确定α。解码是将用于解码水印图像I'的解码。 由计算器S3-S8产生值α'，由加法器S9将偏移值相加，以产生α。 这产生了图像上的α值，其用于缩放数据Ri以隐藏数据。 图像是本发明可应用的材料的一个示例。 产生修正系数值Ci的步骤可以不使用大于阈值T的幅度系数，并且不使用对应的信息符号Ri。 或者，可以设置阈值Tclip。 使用剪切系数值和小于Tclip的幅度系数Ci计算缩放因子α。
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