Handwriting recognition

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Handwriting recognition is the ability of a computer to receive intelligible handwritten 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.

Handwriting recognition principally entails optical character recognition. However, a complete handwriting recognition system also handles formatting, performs correct segmentation into characters and finds the most plausible words.

On-line recognition

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 X(t),Y(t) as well as pen-up/pen-down switching. That kind of data is known as digital ink and can be regarded as a dynamic representation of handwriting. The obtained signal is converted into letter codes which are usable within computer and text-processing applications.

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. By the time of the release of the Newton OS 2.0, wherein the handwriting recognition was greatly improved, including unique features still not found in current recognition systems such as modeless error correction, the largely negative first impression had been made. Another effort was Go's tablet computer using Go's Penpoint operating system and manufactured by various hardware makers such as NCRand 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. This system is distinct from the less advanced handwriting recognition system employed in its Windows Mobile OS for PDAs.

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 has 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.

Off-line recognition

Off-line handwriting recognition involves the automatic conversion of text in an image I(x,y) into letter codes which are usable within computer and text-processing applications. The data obtained by this form is regarded as a static representation of handwriting.

The technology is successfully used by businesses which process lots of handwritten documents, like insurance companies. The quality of recognition can be substantially increased by structuring the document (by using forms).

Handwriting recognition

On-line recognition

Off-line recognition

See also