Online Recognition of Handwritten Telugu Characters

A system for online recognition of handwritten Telugu script is presented. A handwritten character is constructed by executing a sequence of strokes. A structureor shape-based representation of a stroke is used in which a stroke is represented as a string of shape features. Using this string representation, an unknown stroke is identified by comparing it with a database of strokes. A full character is recognized by identifying all the component strokes. Development of similar systems for other Indian scripts is contemplated. 1.0 Introduction Online handwriting recognition consists of recognizing a script as it is written using an electronic stylus or a pen on a tablet. Parameters related to the pen tip like position, velocity, acceleration and sometimes pressure (on the writing surface) are available to the data acquisition system [1,]. Although early work looks back to the sixties, electronic pen devices have gained special attention in the recent times due to the increased demand for more human-like interfaces with the computer [2,3]. Online handwriting recognition takes on a novel significance in the context of Indian languages. Presently, word processing in Indian languages can be a vexing experience, considering the restriction on use of the regular keyboard, designed for English. Elaborate keyboard mapping systems are normally used in case of Indian languages, which are not convenient to use. A comfortable solution would be to let the user write in a natural, normal fashion using a suitable pen-like device and let the computer do the rest. That transfers the burden of learning keyboard mappings from the user to the computer. This is the motivating idea of the present work which describes a system for online recognition of Telugu script, a language most widely spoken in South India. 2.0 The Telugu Character Set Telugu script, as other Indian scripts, is generally written in non-cursive style, unlike English handwriting, which is normally written in cursive style rendering recognition difficult. However, Indian scripts pose a peculiar problem non-existent in European scripts – the problem of composite characters. Unlike in English alphabet where a single character represents a consonant or a vowel, in Indian scripts a composite character represents either a complete syllable, or the coda of one syllable and the onset of another. Therefore, although the basic units that form composite characters of a script are not that many (O(10)), these units by various combinations lead to a large number (O(10)) of composite characters. For example, the word stree, a single syllable comprising three consonant sounds and a vowel, is represented by a single composite character in which graphical elements corresponding to the 3 consonants and the vowel are combined to form a complex structure. Moreover,, Telugu script is the most complex of all Indian scripts for two reasons: a) it has largest number of vowels and consonants and, b) it has complex composition rules. The Telugu script consists of 14 vowels, 36 consonants, 3 special characters. As a general rule when the vowel appears at the beginning of the word, the full vowel character is displayed. When a vowel appears inside a word, a vowel modifier is added to the preceding consonant creating a composite character. The number of combinations possible here to form a composite character is very large. For example,all the above 36 consonants can combine with vowels(i.e. consonant-vowel type approximately 576 in number). Also the 36 consonant modifiers can combine to form composite characters of consonants-consonant-vowel (CCV) type (this number runs approximately to 20,736). Also a character can have more than one consonant modifier (as in stree ). Although rare CCCV type characters are also encountered in Telugu script. Wordprocessing with such a complex script using the QWERTY keyboard can be a harrowing experience, considering the cumbersome keyboard mappings the user has to learn. A pen-based interface in such a situation can prove to be a most convenient tool.