适于移动终端字符识别环境的自适应多阈值二值化方法  

Adaptive Multi-level Threshold Binaryzation Method for Optical Character Recognition in Mobile Environment

作　　者：朱德利[1] 杨德刚[1] 胡蓉[2] 万辉 ZHU De-li;YANG De-gang;HU Rong;WAN Hui(College of Computer and Information Science,Chongqing Normal University,Chongqing 401331,China;College of Computer and Information Science,Southwest University,Chongqing 400715,China)

机构地区：[1]重庆师范大学计算机与信息科学学院,重庆401331 [2]西南大学计算机与信息科学学院,重庆400715

出　　处：《计算机科学》2019年第8期315-320,共6页Computer Science

基　　金：重庆市教委科学技术研究项目(KJQN201800536,KJQN201800521,KJ1600322);重庆市科委基础研究与前沿探索计划(cstc2018jcyjAX0470)资助

摘　　要：为了解决移动终端字符识别应用中光照不均匀、环境不可控而导致的图像二值化效果不佳的问题,提出一种基于积分图快速计算的多阈值自适应二值化方法。该方法首先以待求点为中心设置一个特定尺寸的滑窗,计算该滑窗内所有点的均值,再根据高斯函数加权计算当前滑窗的两个前置滑窗的均值。设置均值松弛因子来衡量当前点的光照情况。像素点的松弛阈值依据该点的松弛因子和光照情况的评价综合计算获得。以Lenovo ZUK Z2 Pro作为实验设备,在Android操作系统中编写程序,进行文字识别精度的测试。所提算法对前景划分的平均召回率为95.5%,平均准确率为91%。调用Tesseract 4.0的原生OCR识别引擎进行验证,在不规则阴影、多层次光照、线性光线变化等环境下,算法的文字识别准确率分别为96.8%,98.2%和93.2%,高于其他预处理算法。所提算法具有较强的鲁棒性和自适应能力,能满足移动终端字符识别应用的图像预处理要求。In order to solve the problem of poor binaryzation quality caused by uneven illumination and uncontrollable environment in OCR applications of mobile terminals,this paper proposed an adaptive multi-level threshold binaryzation method based on integral graph.First,a specific sliding window is set by focusing on the points to be calculated.The normal threshold is the mean value of the sliding window where the current point is located.The two front sliding windows are weighted according to the Gauss function,and then the relaxation factor is obtained according to the weights.The relaxation threshold of pixels are obtained based on the evaluation of the relaxation factor and illumination condition.Experiments were carried out in typical mobile environments such as irregular shadows,multi-level illumination and linear light changes.Lenovo ZUK Z2 Pro is used as the test equipment.The average recall of the algorithm is 95.5%and the average accuracy is 91%.The recognition accuracy of this algorithm is 96.8%,98.2%and 93.2%respectively in the environment of irregular shadow,multilevel illumination and linear light change.The result shows that the proposed algorithm has strong robustness and adaptability,and can meet the requirement of image preprocessing in the OCR application of mobile terminal.

关 键 词：移动终端 图像处理 积分图像 自适应二值化 字符识别 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]