Book scanning

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Book scanning or book digitization (also: magazine scanning or magazine digitization) is the process of converting physical books and magazines into digital media such as images, electronic text, or electronic books (e-books) by using an image scanner.^[1] Large scale book scanning projects have made many books available online.^[2]

Digital books can be easily distributed, reproduced, and read on-screen. Common file formats are DjVu, Portable Document Format (PDF), and Tag Image File Format (TIFF). To convert the raw images optical character recognition (OCR)^[1] is used to turn book pages into a digital text format like ASCII or other similar format, which reduces the file size and allows the text to be reformatted, searched, or processed by other applications.^[1]

Image scanners may be manual or automated. In an ordinary commercial image scanner, the book is placed on a flat glass plate (or platen), and a light and optical array moves across the book underneath the glass. In manual book scanners, the glass plate extends to the edge of the scanner, making it easier to line up the book's spine.^[1][2]

A problem with scanning bound books is that when a book that is not very thin is laid flat, the part of the page close to the spine (the gutter) is significantly curved, distorting the text in that part of the scan. One solution is to separate the book into separate pages by cutting or unbinding. A non-destructive method is to hold the book in a V-shaped holder and photograph it, rather than lay it flat and scan it. The curvature in the gutter is much less pronounced this way.^[3] Pages may be turned by hand or by automated paper transport devices. Transparent plastic or glass sheets are usually pressed against the page to flatten it.

After scanning, software adjusts the document images by lining it up, cropping it, picture-editing it, and converting it to text and final e-book form. Human proofreaders usually check the output for errors.

Scanning at 118 dots/centimeter (300 dpi) is adequate for conversion to digital text output, but for archival reproduction of rare, elaborate or illustrated books, much higher resolution is used.^{[citation needed]} High-end scanners capable of thousands of pages per hour can cost thousands of dollars, but do-it-yourself (DIY), manual book scanners capable of 1200 pages per hour have been built for US$300.^[4]