Human interaction with digital ink : legibility measurement and structural analysis
Abstract
Literature suggests that it is possible to design and implement pen-based computer
interfaces that resemble the use of pen and paper. These interfaces appear to
allow users freedom in expressing ideas and seem to be familiar and easy to use.
Different ideas have been put forward concerning this type of interface, however
despite the commonality of aims and problems faced, there does not appear to be
a common approach to their design and implementation.
This thesis aims to progress the development of pen-based computer interfaces
that resemble the use of pen and paper. To do this, a conceptual model is proposed
for interfaces that enable interaction with "digital ink". This conceptual model is
used to organize and analyse the broad range of literature related to pen-based
interfaces, and to identify topics that are not sufficiently addressed by published
research. Two issues highlighted by the model: digital ink legibility and digital
ink structuring, are then investigated.
In the first investigation, methods are devised to objectively and subjectively
measure the legibility of handwritten script. These methods are then piloted in
experiments that vary the horizontal rendering resolution of handwritten script
displayed on a computer screen. Script legibility is shown to decrease with rendering
resolution, after it drops below a threshold value.
In the second investigation, the clustering of digital ink strokes into words is
addressed. A method of rating the accuracy of clustering algorithms is proposed:
the percentage of words spoiled. The clustering error rate is found to vary among
different writers, for a clustering algorithm using the geometric features of both
ink strokes, and the gaps between them.
The work contributes a conceptual interface model, methods of measuring
digital ink legibility, and techniques for investigating stroke clustering features, to
the field of digital ink interaction research.