The present disclosure relates to advanced image processing and encoded signal processing. One claim recites an image processing method comprising the acts: receiving a digital representation of product packaging artwork, comprised of pixels; defining a guard band region surrounding text characters included in the artwork, in which a first region encloses the guard band region, and a second region encloses the first region; and altering the artwork to redundantly encode a machine-readable plural-bit payload across different regions of the artwork. The altering only alters the artwork outside of the guard band region, wherein a strength of the encoding has a first value in the first region, and has a second, stronger, value in the second region. Of course, other claims and combinations are described as well.