A printed image can be redundantly encoded by printing a visible image using a colorant with a luminance that contrasts with that of the output sheet and printing a redundant image using a colorant with a luminance that varies only slightly from that of the output sheet. Accordingly, the visible image can be easily read by a user while the redundant image is substantially invisible to the human eye at normal-reading distances, yet capable of being captured by a conventional digital scanner. In one aspect, redundantly encoded images may be printed on a white background, with visible images printed in black text and redundant images printed in blue in content regions of the visible image and in yellow in its background regions.