Research And Realization Of License Plate Characters Recognition Algorithms

With the rising demand for transport, license plate recognition technology based on image processing is an important means of solving the problems of traffic violations, monitoring, fees, and so on. For image acquisition, preprocessing, character segmentation and character recognition, the article describes detailed theories and analyzes the merits and shortcomings of the traditional methods. At last, the author puts forward the improved algorithms combined the merits of the traditional algorithms, and experimental results are showed.Because the traditional Berson, Ostu ways are easy to be disturbed by the noise. The author improves the Ostu way and presents the way of dynamic threshold value based on Ostu. It overcomes the shortcomings of traditional binaryzation ways, and combines the merits of them. The new algorithm has used the different threshold values in different regions, so it can effectively suppress the disturbance of the complex illumination environment and greatly reduce noise participation, then it has provided a good car license image environment for the following segmentation work. In the charaters division module, the author improves the traditional projection way and proposes the thought of calculated the characters outset coordinate, then proposes the coordinate marking algorithm. This algorithm can effectively overcome the influence of noises, the character adhesion and break, and characters can be correctly divided. At last, in characters recognition module, the author improves the way of traditional template matched and presents the thought of extracted the characters structural and statistical natures, proposes the template matched way based on the structural features and the statistical natures. Firstly, the algorithm extracts the structural features of the numbers and the letters to carry on the thick classification. Secondly, it extracts the statistical natures of Chinese character and the rest characters, such as: the characteristic values of scanned in line and row, and line and row projection values, and the horizontal and vertical widths. The new way combines various characteristics of binaryzation character to compose the respective templates, moreover, it extracts some characteristics of special characters to expand character recognition scope. Finally, license plate characters are matched with templates to get correct recognition result.In order to confirm the accuracy and effectivenesss of the above algorithms, massive programming experimental work have been done in several parts of the car license image binaryzation, character segmentation and recognition. All of the algorithms are implemented in VC++, and experiments prove that the improved algorithms have a better effect. The author has made the beneficial attempt to improve character recognition speed and accuracy, and has made own effort to enhance the performance of the vehicles car license recognition technology.