1. A computer-implemented method for generating a variable density mono-color under-print layer corresponding to an image to be printed, the method comprising: receiving a printable image, the printable image comprising a plurality of first pixels; generating, by one or more processors, a mono-color under-print layer, the mono-color under-print layer comprising a plurality of second pixels, each second pixel corresponding to a first pixel in a same corresponding position in the printable image and each second pixel having an associated opacity whose value is based on at least one color characteristic of its corresponding first pixel.