Paper Conservation: Decisions & Compromises

Applications of Image Processing Software to Archival Material
Christina Duffy
The British Library, London, UK
Introduction
Images of archival material are useful to both
conservators for monitoring changes and to researchers
for detailed analysis and permanent
access to collection items. Digitisation projects
generate huge volumes of image data. Images
can be enhanced and manipulated with image
processing software to suit the specific needs of
the user. This allows historical documents and
other collection items to be studied without the
risk of damage to the primary source.
ImageJ is a powerful public domain Java-based
image processing package. The nature of open
source software allows for the constant update
and availability of new plugins and recordable
macros designed for specific tasks. ImageJ’s
built-in editor and a Java compiler allow for the
development of custom acquisition, analysis and
processing plugins.
In this study the applications of image processing
software to archival material are described
highlighting the wealth of information
that can be obtained from images.
ImageJ
ImageJ was originally designed for the purpose
of medical imaging by the National Institutes for
Health by Wayne Rasband, but has since found
applications in many fields. It can be run on any
computer with a Java 5 or later virtual machine,
as an online applet or as a downloadable application
(Microsoft Windows, Mac OS, Mac OSX,
Linux, Sharp Zaurus PDA).
ImageJ offers features similar to commercially
available image processing software packages
such as brightness/contrast adjustment, frequency
domain filtering, binarisation and particle
analysis.
ImageJ Applications to Cultural Heritage
1.Image File Distribution
File Format Conversions: The sharing and distribution
of large image files generated by digitisation
projects is often hampered by both the sender
and recipient’s ability to convert between file
formats. ImageJ is a versatile image processing
program which can open and convert between
TIFF, GIF, JPEG, PNG, DICOM, BMP, PGM and FITS
images. Plugins can be installed to allow RAW
image files, images in ASCII format and images
which are loaded over the network using an URL
to be opened and manipulated. This versatility
allows any image format to be converted into the
users preferred format for storage and archival
purposes.
2. Digital Image Enhancement
Brightness/Contrast Adjustment: Important features
in a collection item are often obscured due
to poor environment lighting during image capture.
ImageJ supports 8-bit, 16-bit and 32-bit grayscale
images, and 8-bit and 32-bit colour images.
The brightness and contrast of an image can be
interactively altered serving to optimise features
and enhance regions which are shrouded in
darkness (Fig. 1).
However, when the brightness and contrast
of the original image is altered, information is
lost; the modified image has a reduced greyscale
range. Therefore although the modified image
appears more pleasing to the human eye (i.e. the
differences between foreground and background
seem more evident), the original actually contains
more information and is of a higher quality
(Faigenbaum et al. 2012).
Fig. 1
3. Metadata Generation
Set and apply scale: Accurately recording the
size of a collection item is an important part of
metadata documentation. ImageJ can be used to
ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013
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