Handwriting Recognition
Handwriting recognition refers to the ability of
a computer to receive intelligible written
input. The image of the written text may be
sensed "off line" from a piece of paper by
optical scanning (optical character
recognition). Alternatively, the movements of
the pen tip may be sensed "on line", for example
by a pen-based computer screen surface. The
elements of an on-line handwriting recognition
interface typically include:
a pen or stylus for the user to write with.
a touch sensitive surface, which may be
integrated with, or adjacent to, an output
display.
a software application which interprets the
movements of the stylus across the writing
surface, translating the resulting curves into
digital text.
Handwriting recognition is commonly used as an
input method for PDAs. The first PDA to provide
written input was the Apple Newton, which
exposed the public to the advantage of a
streamlined user interface. However, the device
was not a commercial success, owing to the
unreliability of the software, which tried to
learn a user's writing patterns. Another effort
was Go's tablet computer using Go's Penpoint
operating system and manufactured by various
hardware makers such as NCR and IBM. IBM's
Thinkpad tablet computer was based on Penpoint
operating system and used IBM's handwriting
recognition. This recognition system was later
ported to Microsoft Windows for Pen, and IBM's
Pen for OS/2. None of these were commercially
successful.
Palm later launched a successful series of PDAs
based on the Graffiti® recognition system.
Graffiti improved usability by defining a set of
pen strokes for each character. This narrowed
the possibility for erroneous input, although
memorization of the stroke patterns did increase
the learning curve for the user.
A modern handwriting recognition system can be
seen in Microsoft's version of Windows XP
operating system for Tablet PCs. A Tablet PC is
a special notebook computer that is outfitted
with a digitizer tablet and a stylus, and allows
a user to handwrite text on the unit's screen.
The operating system recognizes the handwriting
and converts it into typewritten text. Notably,
Microsoft's system does not attempt to learn a
user's writing pattern and instead maintains an
internal recognition database containing
thousands of possible letter shapes.
In recent years, several attempts were made to
produce ink pens that include digital elements,
such that a person could write on paper, and
have the resulting text stored digitally. The
success of these products is yet to be
determined.
Although handwriting recognition is an input
form that the public had become accustomed to,
it has not achieved widespread use in either
desktop computers or laptops. It is still
generally accepted that keyboard input is both
faster and more reliable. On PDAs, the Graffiti
system is being phased out in favor of
keyboards.
On-line handwriting recognition
involves the automatic conversion of text as it
is written on a special digitizer or PDA, where
a sensor picks up the pen-tip movements Xt,Yt as
well as pen-up/pen-down switching. The obtained
signal is converted into letter codes which are
usable within computer and text-processing
applications. However, the classification of
characters is just one of the functions of a
complete on-line handwriting recognition system.
A complete system needs to preprocess the often
noisy signal, find a proper segmentation into
characters and find the most plausible words.
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