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.