Digital File Formats for Digital Preservation

Introduction

In the process of digital preservation, file formats play very important role. These are the standards which incorporate the quality issues relating to information storage, file size, type of data compression and also information retrieval. Since we are moving towards ‘Paperless society’, the functions and strategies for achieving the basic objectives have been changed in modern Library and Information Centre. The same principal applies to the managers of archive drawings and photographic records, who have the facilities for the storage of their archives in digital format. The conversion of the original hard copy records into digital records is known as digitization. In the process of digital preservation, it is primarily essential to examine basic issues to achieve the required end product. For line drawings the question needs to be asked as to whether the drawing is likely to be used and modified or is retained as an archive. If it belongs to an archival collection, the drawing is scanned and stored as a digital file on CD-ROM or DVD. If the drawing is to be used as a working drawing on a Computer Aided Design (CAD) system, then the scanned data needs to be converted into vector data in an intelligent form i.e. in a way that replicates the same drawing if it had been produced originally on CAD.

Photographs are also scanned using the original negatives or transparencies if possible, if not then photographic prints. Old and damaged photographs can be cleaned and digitally repaired.

Three major issues related to storage of Digital information:

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  The format of the digital data and any compression has a major effecting file size and a minor effect on quality.

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  The resolution of the scanning is a balance between quality and file size.

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  The storage medium can have an effect on retrieval times.

As computer storage is becoming less expensive, it supports to move towards higher standards, i.e. higher resolution. But it should be remembered that a relatively small increase in the resolution results in a proportionately high increase in file size.

Several raster-based file formats are available to store digitized information. Several new image file formats are also emerging. Many are limited to particular applications, such as digital capture devices or image manipulation programs. Others are destined for wider use, with their developers intending them to become official or de facto standards. It is a long and difficult process to create such standard formats and longer still for them to become widely used and supported (Ingels, 1976).

Presently we have mainly six formats, which may be divided into two categories:

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  Open (Non-Proprietary) Formats: TIFF, PNG, GIF and JPEG etc.

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  Close (Proprietary) Formats: MrSID, DjVu, Genuine Fractals and Pixel Live/ VFZoom etc.

Detailed description of some of the prominent file formats is as follows:

Open (Non-Proprietary) Formats

Any digitization project will need to consider the long-term usefulness and accessibility of the images and this means choosing a file that is both an established industry ‘standard’ as well as a non-proprietary format. Some of these formats are discussed below: