No matter where a book lover travels, they can automatically be accompanied by digital versions of many of their favorite books from their home collections through Shelfie, a new mobile app that helps users acquire free or inexpensive digital versions of a wide variety of print books.

Shelfie lets users take smartphone photographs of each bookshelf in their home or work libraries, which are then scanned using computer vision and special algorithms that read the titles of the books and enter them into a user's personal database. Once the lists of books in their collections are created, Shelfie can then identify which titles offer free digital versions that can be added to a user's device. Using the technology, users can always have those books with them in digital form for ready reference or reading, wherever they are, Peter Hudson, co-founder and CEO of the company, told eWEEK.

"Shelfie recognizes about 43 million different book spines" for titles, said Hudson. "We literally spent about three years working on the algorithms to segment the spines on book shelves into individual book spines" for use by the app. It's like the Shazam music recognition app for finding song titles and artists, said Hudson, only this app is aimed at book lovers.

Scanned book titles that don't have free digital versions are identified to users, who may be able to select and purchase inexpensive digital versions of some titles for one to three dollars typically. Text books can be priced at $9.99 or more in digital form.

All books in a user's collection will be identified, but only about 25 percent so far will be found to have free or inexpensive digital versions, according to Hudson. The rest of the books may be old or simply don't have digital versions from participating publishers at this point, he said.

The app also provides book recommendations for users based on the titles they own and how they group their books on their shelves, so they can learn of other titles that may pique their interest. Recommendations are also made based on the book collections of other users of Shelfie. Book collections of friends and other users are also visible through the app so that readers can get insights into other books they might want to read.

So far, Shelfie has signed digital content deals with three of the Big 5 publishing companies—HarperCollins, Macmillan and Hachette—to offer Shelfie users free or discounted versions of their personal books. Still unsigned are Simon & Shuster and Penguin, said Hudson. Some 400,000 books so far are eligible for free or inexpensive digital acquisitions through the app.

The idea for Shelfie was inspired in June 2012 as Hudson was having a conversation with a friend who quoted a favorite passage of a book about quantum computing. The friend said he could imagine the page of the book in his mind and he wished he had it with him at that moment to show it to Hudson.

"Both of us stared at each other and said 'That's crazy. Why doesn't this exist for books?'" he said.

They each used their smartphones to search online to see if such an app existed, and when one couldn't be found, an idea was born—to come up with a way to carry digital copies of favorite books, wherever a user is at that moment, said Hudson. That could be while on vacation at the beach, while traveling abroad or even when visiting relatives.

"Eleven days later, I sold my motorcycle and began the work on the app," he said.

The app works using computer vision, which is a subfield of artificial intelligence or machine learning, said Hudson. "The challenge with computer vision is it can't recognize things like a model of Eiffel Tower versus a photo of the real thing."

With books, however, computer vision works well because they have a finite number of viewable angles, making them easier to identify, he said.

To capture images, users must take their photos using the app on a shelf by shelf basis in a landscape mode, with the height of the books filling the screen so the images are as accurate as possible. The app automatically fires the flash on the smartphone to better illuminate the images, even if the flash is turned off.

The free app, which is so far available only in English, was launched in December in versions for iOS or Android. It can be used on smartphones and tablets.