Adaptive Median Filtering Algorithm Based on Divide and Conquer and Its Application in CAPTCHA Recognition

作     者：Wentao Ma Jiaohua Qin Xuyu Xiang Yun Tan Yuanjing Luo Neal NXiong 

作者机构：College of Computer Science and Information TechnologyCentral South University of Forestry&TechnologyChangsha410114China Department of Mathematics and Computer ScienceNortheastern State UniversityOklahoma74464USA. 

出 版 物：《Computers, Materials & Continua》 (计算机、材料和连续体（英文）)

年 卷 期：2019年第58卷第3期

页      面：665-677页

核心收录：

学科分类：08[工学] 0812[工学-计算机科学与技术（可授工学、理学学位）] 

基　　金：This work is supported by the National Natural Science Foundation of China(No.61772561) the Key Research&Development Plan of Hunan Province(No.2018NK2012) the Postgraduate Research and Innovation Project of Hunan Province(No.CX2018B447) the Postgraduate Science and Technology Innovation Foundation of Cent ral South University of Forestry and Technology(20183027) the Key Laboratory for Dig ital Dongting Lake Basin of Hunan Province 

主　　题：Image preprocessing machine learning CAPTCHA recognition adaptive median filtering algorithm. 

摘      要：As the first barrier to protect cyberspace,the CAPTCHA has made significant contributions to maintaining Internet security and preventing malicious *** researching the CAPTCHA,we can find its vulnerability and improve the security of ***,many studies have shown that improving the image preprocessing effect of the CAPTCHA,which can achieve a better recognition rate by the state-of-theart machine learning *** are many kinds of noise and distortion in the CAPTCHA images of this *** propose an adaptive median filtering algorithm based on divide and conquer in this ***,the filtering window data quickly sorted by the data correlation,which can greatly improve the filtering ***,the size of the filtering window is adaptively adjusted according to the noise *** demonstrated in the experimental results,the proposed scheme can achieve superior performance compared with the conventional median *** algorithm can not only effectively detect the noise and remove it,but also has a good effect in preservation ***,this algorithm can be one of the most strong tools for various CAPTCHA image recognition and related applications.