Abstract: The basic process of vehicle license plate location includes pretreatment, the rough
location and the accurately location of license plate. In the step of the rough location, the traditional
license plate locating algorithm based on mathematical morphology, and the key to its success is the
selection of the structural element. Generally, we use the same structural elements to determine the
location of license plate. But there are some faults. An algorithm based on adaptive row and columns
structure element of mathematical morphology is proposed. Under natural conditions, the location of
license plate in vehicle image may be effected by the brightness or darkness. Based on this, the
adaptive contrast enhancement algorithm is proposed in this paper which is applied in the image
pretreatment stage. The results show that the algorithm is effective. In the step of precise positioning,
this paper used method of region-labeling and the method of projection to locate the license plate
accurately. We collect more than six hundred images in different time or place and experiment results
show that the method is effective.

Key words: license plate location, morphology, adaptive, structural element, region-labeling, projection method