1. A method of embedding a digital watermark in a digital image, comprising: generating an image adapted to be applied to an object based on the digital image, including: converting the digital image to at least one halftone image; and embedding an auxiliary signal in the digital image so that the auxiliary signal is substantially imperceptible, yet machine readable; and encoding a message in the auxiliary signal that includes halftone information, wherein the halftone information is configured to be automatically readable from a printed version of the image to enable checking whether measured attributes of the printed version of the image correspond to the halftone information.