An Adaptive Algorithm for Automatic License Plate Orientation
一种自适应车牌图像定位新方法

An adaptive algorithm for license plate(LP) orientation was proposed. Based on the common features of LP, the vertical edge was first detected. Then, some approaches were adopted to remove adaptively the invalid edge due to the characteristics of vertical texture and edge density, so that the regions with features of LP were preserved. Next, horizontal morphologic operation was conducted to close the candidate regions, and the above method overcomes the problem how the morphologic structure element was adjusted adaptively to the size change of LP. A viewpoint then proposed was that the gray adjustment and color recognition modules could be employed according to actual scene conditions. With abundant samples verified in dark hours and daytime in real conditions, the experiment indicates that it is feasible to adopt this algorithm in LP recognition system to achieve both accuracy and adaptability.