Watermark detection in an image or the like can be optimized by exploiting
the innate biases in the image to emphasize the watermark signal. The
watermark signal can be trial-located with different origins in the image
to find one that yields improved results. Similarly, the image can be
processed (e.g., by changing resolution, rotation, or compression) so as
to change the innate biases to better reinforce the watermark signal.
Compression of an image can be done in accordance with a desired
identifier, with the compressor deciding which image components to retain
and which to discard based, in part, on the identifier that is to be
associated with the image. The techniques are also applicable to other
forms of content, such as audio. A variety of other arrangements are also
detailed.