License Plate Number Recognition - New Heuristics and a Comparative Study of Classifiers

We describe an artificial vision system used to recognize the Spanish car license plate numbers in raster images. The algorithm is designed to be independent of the distance from the car to the camera, the size of the plate number, the inclination and the light conditions. In the preprocessing steps, the algorithm takes a raster image as input and gives an ordered list of license plate areas candidates. Only in very rare occasions the second and third candidates are needed; most of the cases the first candidate is the correct one. During the preprocessing a new filter has been used. This filter is only applied to low saturation areas, getting better results this way. In order to choose the best classifier for the classifying stage, a comparative study has been performed using the data mining tool Weka.