Handwritten Character Recognition

Handwriting Detection is a technique or ability of a Computer to receive
and interpret intelligible handwritten input
from source such as paper documents, touch screen, photo graphs etc.
Way to Recognize
Handwriting
Intelligent Word
Recognition
Optical Character
Recognition

Database
with samples of known
authorship
Identification
System
Writer 1
Writer n

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 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:
1) a pen or stylus for the user to write with.
2) a touch sensitive surface, which may be integrated with, or adjacent to,
an output display.
3) a software application which interprets the movements of the stylus
across the writing surface, translating the resulting strokes into digital text.

Off-line handwriting recognition involves the automatic
conversion of text in an image 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. Off-line handwriting
recognition is comparatively difficult, as different people
have different handwriting styles. And, as of today, OCR
engines are primarily focused on machine printed text and
ICR for hand "printed" (written in capital letters) text.
There is no OCR/ICR engine that supports handwriting
recognition as of today.

• Recognition strategies heavily depends on the nature
of the data to be recognized.
• In the cursive case, the problem is made complex by
the fact that the writing is fundamentally ambiguous
as the letters in the word are generally linked
together, poorly written and may even be missing.
• On the contrary, hand printed word recognition is
more related to printed word recognition, the
individual letters composing the word being usually
much easier to isolate and to identify.
Continue..

• Character Recognition techniques can be classified according
to two criteria:
– the way preprocessing is performed on the data
– the type of the decision algorithm
• Preprocessing techniques include :
– the use of global transforms (correlation, Fourier descriptors, etc.)
– local comparison (local density, intersections with straight lines,
variable masks, etc.)
– geometrical or topological characteristics (strokes, loops, openings,
diacritical marks, skeleton, etc.)
• Decision methods include:
– various statistical methods,
– neural networks, structural matching (on trees, chains, etc.)
– stochastic processing (Markov chains, etc.).

• Two main types of strategies have been applied to this
problem:
– the holistic approach - recognition is globally performed on
the whole representation of words and there is no attempt
to identify characters individually.
• The main advantage of holistic methods is that they avoid word
segmentation
– the analytical approach - deal with several levels of
representation corresponding to increasing levels of
abstraction (usually the feature level, the grapheme or
pseudo-letter level and the word level). Words are not
considered as a whole, but as sequences of smaller size
units which must be easily related to characters in order to
make recognition independent from a specific vocabulary

Feature extraction works in a similar fashion to neural network recognizers
however, programmers must manually determine the properties they feel
are important.
Some example properties might be:
Aspect Ratio
Percent of pixels above horizontal half point
Percent of pixels to right of vertical half point
Number of strokes
Average distance from image center
Is reflected y axis
Is reflected x axis

Different stages of handwriting segmentation.
(A) (B) (C)
Images of authentic handwriting sample.
IBM TransNote works based
on two Features…
1) Handwriting Speed
2) Handwriting Wrinkliness

Statistical Experiments
Wrinkliness calculation: a) handwriting
sample, b) edge-detected sample, c) portion of edgedetected
sample at 300 dpi, d) portion at 600 dpi.
A sample of the calculated measurements.
Filename 300dpi 600dpi Wrinkliness Speed
0101T1 14894 30583 1.03799867 0.11396973
0101T2 8786 18638 1.084968652 0.107457204
0101T3 9258 19764 1.094102493 0.118184103
0202T1 6453 13765 1.092962679 0.093275242
0202T2 6212 13319 1.100356033 0.094080635
0202T3 5824 12722 1.127243231 0.087968122

• Handwriting Recognition aims to design systems
which are able to recognize handwriting of natural
language
• Methods and recognition rates depend on the level
of constraints on handwriting.
• The constraints are mainly characterized by the:
– types of handwriting
– number of scriptors
– size of the vocabulary
– spatial layout.
Continue..

Segmentation problem
(can't read word until
it is segmented; can't
segment word until it is read)
– Different handwriting styles
– Use of dictionary to correct
for errors in reading
nr?
m?
Srnitb --> Smith

Outlines of word are traced and smoothed:
Handwriting slope is corrected for automatically:

• Goal: robustly cut letters into segments
• Match multiple segments to detect letters
• Easier than matching whole letter

ADVANTAGES:
The most important advantage of speech
over handwriting is the speed of data entry. This is because it is much easier to
dictate the
machine than to write
DISADVANTAGES:
Has also drawbacks, such as it is noisy to hear
someone sitting next to us and talking to his machine. Moreover, anyone who
wants to input
confidential data to his/her computer is not willing to do it in public places. Most
importantly, it
is not possible to speak to a machine in a natural way due to constraints such as
out of vocabulary
wards, background noise, cross-talk, accented speech and so on.

So after all these stuff…
We have a brief Idea about Automatic Handwriting
Detection..
1) online and offline detection is available
2)Online procedure is easier then Offline procedure(difficult
one)
3)Today’s business world need some computerized
authentication for security purpose
the (AHD) fulfill their need.
4)Handwriting recognition is important for genealogy...
...but it is hard
5)Current methods don't work very well...
...and they don't operate much like the human brain

Handwritten Character Recognition

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