针对不同尺寸车牌图像的定位问题，提出了一种新的自适应车牌定位方法。该方法首先根据车牌区域的共性来提取图像的纵向边缘；然后由车牌区纵向纹理和边缘密度等特征，采用一系列步骤自适应去除干扰边缘来保留类车牌特征区域；最后通过横向形态学运算使类车牌区闭合，以有效地克服以往形态学结构元素难以随车牌尺寸变化自适应选取的问题；同时提出了根据场景实际情况，选用灰度调整和颜色来判别模块的观点。通过实际场景中大量车牌样本的验证结果表明，该算法不仅准确率较高，而且自适应性良好，具有实用价值。

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.