A multiplicative colour watermark.
Ron G. van Schyndel, Andrew Z. Tirkel, Imants Svalbe · 1999
Digital watermarks are imperceptible signals additively embedded in image, video or audio data. Ongoing research has largely concentrated on embedding watermarks in scalar data. Here we introduce a non-linear watermarking scheme for multi-variate data that deliberately perturbs an angle formed between associated variables. Our application embeds a spread-spectrum based watermark in the hue component of transformed RGB colour image data. This watermark, being additive in the angular domain, is multiplicative in the data domain. This contrasts with other spread-spectrum based watermarking schemes. 1.