A Generalized Approach to Amharic Braille Recognition
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Date
2015-06-08
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Addis Ababa University
Abstract
In 1825 Louis Braille invented the writing system braille which is the preferred means of
written communication for blind people around the world. In Ethiopia, there has been a large
production of Amharic braille documents from the time of its introduction in 1934. Since
Braille documents are usually read and understood only by visually impaired and those others
who have learned braille only, their literatures are highly restricted from reaching the sighted
society. Optical Braille Recognition (OBR) is an important technology to bridges the
communication gap that exists between the blind and the sighted people. In addition, OBR
serves as a technology to preserve documents that only exist in Braille form and can also
serve as a simple mechanism for braille copy.
Past researches carried out locally have made an attempt to develop an ABR system for
Amharic braille recognition. There were also some efforts made to improve the performance
of the Amharic ABR system. As a continuation to those previous efforts, this research
presented an approach for recognition of double-sided Amharic braille documents. In this
regard, image thresholding and segmentation techniques are explored and adopted in this
work with some improvements.
An adaptive thresholding algorithm that uses the pixel values on every image is used to
compute two threshold values that segment the Braille image into bright, dark and
background. A moving window scanning technique that scan every column of an image and
extract the dot regions for the front and back side of the image and put them into two separate
arrays is also adopted and improved. In addition, an improved grid construction technique is
designed that automatically determines the average dot area and exclude dots which are
smaller or bigger in size that can affect the performance of the grid construction. The grid
construction process has incorporated techniques for refining itself when any error exists.
Braille cells are formulated by using the location of six intersection points in the constructed
grid. Finally, a lookup table is developed for every character in Amharic and features of
braille cells are matched against corresponding Amharic print characters.
The system is tested using database from scanned clean, average noisy and high level noise
Amharic braille documents. The developed system works with 100% accuracy for both
single-sided and double-sided clean braille documents. However, as the level of noise
increases the performance of that system fails. Overall, an accuracy level of 99.27% for
xi
single-sided and 88.16% for double-sided braille documents is achieved. Degradation of
braille document and skewness has been the major challenges. The results achieved show that
the work is promising. However, to further improve the system, areas that need further
consideration in future such as improved image filtering, skew angle correction, format
preservation and post recognition correction are recommended
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Keywords
Amharic Braille Recognition