The Indigo seven-color digital presses have been set up at Amazon’s US fulfillment centers where they are now producing full-color books on demand, as well as color covers for black and white books.

Amazon’s on-demand service draws on various digital assets hosted by the company in PDF or other file formats and is designed to cater to the vanity publishing and print-on-demand photobooks market but also to meet other occasional requests for small-volume or rare out-of-print books.

HP’s is claimed to be the only digital press on the market which uses liquid ink to produce high-quality images that can rival the offset print methods used in the book publishing world.

The Indigo system is intended to match offset in quality, but be more flexible in terms of run size, said Paul Randall of HP’s Indigo business. It sits just below the threshold of what is practicable using traditional offset litho machines and offers the short run, high-quality capability which is required for full color work.

The books-on-demand market is expected to grow double in size by 2009.