| 摘要 |
A scheme for inserting and extracting an invisible fragile watermark in an image/video sequence, in order to verify whether a watermarked image has been tampered with. According to one aspect of the invention, there is provided a method of watermarking a digital image, comprising: obtaining digital image coefficients; forming a plurality of arrays of image coefficients, each array comprising a predetermined number of image coefficients, the image coefficients comprising coefficients with first, second and third values; and for each array determining a binary value as a watermark component bit; determining a quantization parameter, based on the separation between the first and second values; selecting a plurality of values to represent ones and zeros, the separation between successive selected values being determined on the basis of the quantization parameter; and modifying the third value, such that it takes the closest one of the selected values which represents the determined watermark component bit. According to another aspect of the present invention, there is provided a method of extracting a watermark embedded in that way. |
