The present disclosure relates generally to signal processing, including processing digital watermarking. One claim recites a detector apparatus comprising: memory for storing data representing color image data comprising red color data and green color data, in which the red color data comprises digital watermarking including a first polarity and the green color data comprises the digital watermarking including a second polarity that is inversely related to the first polarity; means for selectively weighting the red color data and the green color data so that the digital watermarking is emphasized while image content is de-emphasized when weighted red color data and weighted green color data are combined; means for detecting the digital watermarking from combined, weighted red color data and weighted green color data; and more or more processors configured for outputting data corresponding to detected digital watermarking. Of course, different combinations and claims are provided too.