Digital watermark
From The Glossary of Digital Photography
A way of marking an image to indicate ownership or copyright information. This watermark can be visible or invisible. A visible watermark often comes in the form of a logo or copyright information, or website and contact information. An invisible watermark is built into the data of the image so that it can't be seen but can be detected by special software. Creating invisible watermarks requires a technique called steganography. Invisible watermarking is useful for identifying the ownership of an image or for finding it. See also Digimarc; steganography
