Using your encoded images in print
A primary consideration in placing images is to avoid scaling. You should scale images to their final size before watermarking. Reducing or enlarging an image more than 10% after embedding the watermark can adversely affect watermark detectability.
Cameras without auto-focus, aperture controls, and high quality image sensors have difficulty resolving fine details. Reducing an image more than 10% can push it beyond the capabilities of such cameras to resolve enough detail to detect the watermark.
Enlarging an image can create the opposite problem of reduction. If you excessively enlarge an image, significant portions of the watermark will fall outside the camera’s field of view, and the watermark can be cropped beyond detectability.
Another issue with scaling images is that watermarks are designed to be read at approximately 7 to 15cm ( 3″ to 6″), and users will quickly adapt to these boundaries. Reduced or enlarged images may contradict users’ expectations about where to hold their devices, even if their cameras are capable of watermark detection at shorter or longer distances.