A technique for watermarking an image and a resulting 'watermarked' image

摘要

Apparatus and an accompanying method, for generating a "watermarked" image; for subsequently detecting that watermark in a test image; and the watermarked image so formed. First, pixel values for a non-marked image are transformed, into a series of transform coefficients. A set of pseudo-random perturbation values is determined, such that all these values collectively satisfy a plurality of different mathematical constraints. These perturbation values are then added to the transform coefficients. Resulting perturbed coefficients are then inversely transformed to form the watermarked image. To detect the watermark a plurality of different mathematical tests are then used, in conjunction with the perturbation values.