车牌图像的可视性增强与倾斜校正研究

发布时间：2018-02-19 22:05

  本文关键词： 图像去噪 核范数最小化 车牌倾斜 低秩纹理 仿射变换　出处：《合肥工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来交通需求的日益增大,道路交通存在的矛盾越来越尖锐,交通的智能化是整个交通生态环境中必不缺少的一课。而其中应用最广的自动车牌识别技术更是重要的一环,为了给车牌识别提供更有质量的图像源,文章研究其中两个方面的问题,即车牌图像的可视性增强和倾斜校正。首先在车牌图像的可视性增强方面,本文主要针对图像的噪声以消除其所带来的视觉影响。在图像去噪非局部框架中,利用低秩模型的核范数最小化并将图像的先验信息用权重系数的手段体现出来。文章中利用了矩阵较大奇异值在作用上具有高优先级这一性质并给较大奇异值赋予较小权值以达到较小的收缩,提出加权核范数最小化图像去噪方法。通过实验论证,该方法在主观视觉上整体和细节都获得了较之前方法的优势,而且其峰值信噪比也得到了较高的值。车牌识别中的另一方面,图像倾斜同样是字符分割乃至识别中重要的一步。基于此,提出一种适用范围更广的基于低秩纹理变换不变性的车牌倾斜校正方法。先将车牌图像看成一个矩阵,然后利用对称规则结构的低秩特性把经过旋转、仿射等变换的图像恢复成低秩纹理。根据不同的环境条件,对随机拍摄的倾斜车牌图像进行校正,实验表明即使面对一些如无边框、车牌污染、环境光遮蔽、噪声大等恶劣条件,文章的方法也得到了出色的校正结果。文章提出了一种借助于图像整体信息进行倾斜校正的新思路,由于该方法摒弃了以往的从角点、边缘等局部特征的角度,因此具有更高的精确度和鲁棒性。实验结果也证实了文章中方法的有效性且满足整个识别系统的实时要求。
[Abstract]:In recent years, with the increasing demand for traffic, the contradiction of road traffic is becoming more and more acute. The intelligent traffic is a necessary lesson in the whole traffic ecological environment, and the most widely used automatic license plate recognition technology is an important part. In order to provide a better quality image source for license plate recognition, two problems are studied in this paper, namely, the visibility enhancement and tilt correction of license plate image. This paper mainly aims at the noise of image to eliminate the visual influence. In the non-local frame of image denoising, The kernel norm of the low rank model is minimized and the prior information of the image is represented by the weight coefficient. In this paper, the property that the larger singular value of the matrix has a high priority in action is used and the larger singular value is assigned to the larger singular value. To give a smaller weight value to achieve a smaller contraction, A weighted kernel norm minimization method for image denoising is proposed. The experimental results show that the proposed method has the advantages of both overall and detailed subjective vision. On the other hand, image tilt is also an important step in character segmentation and recognition. In this paper, a more widely used method for license plate tilt correction based on the invariance of low rank texture transform is proposed. Firstly, the license plate image is regarded as a matrix, and then the image is rotated by using the low rank characteristic of the symmetric regular structure. The image of affine transform is restored to low rank texture. According to different environmental conditions, the random image of inclined license plate is corrected. The experiment shows that even in the face of some things such as no border, license plate pollution, environmental light masking, In this paper, a new method for skew correction with the help of the whole information of the image is proposed, because the former corner point is abandoned by this method. Because of the angle of local features such as edges, it has higher accuracy and robustness. The experimental results also show that the proposed method is effective and meets the real-time requirements of the whole recognition system.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP391.41
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本文编号：1518097