一种扭曲粘连字符验证码识别方法

摘要

The study of CAPTCHA recognition can discover CAPTCHA security vulnerabilities in time to make it more secure. Distorted and merged CAPTCHA can resist character segmentation, which is the difficult in CAPTCHA recognition. An approach based on DENSE SIFT and RANSAC algorithm is presented for recognition of distorted and merged CAPTCHA. Firstly, matching set is obtained through the matching of DENSE SIFT. Then, matching information is got by using RANSAC algorithm. Finally, recognition results are acquired by means of queue-analysis algorithm. The experimental results show that the proposed method has good performance on CAPTCHAs in different levels of difficulty.%验证码识别研究能及时发现验证码的安全漏洞，使其变得更加安全。扭曲粘连字符验证码能抵抗字符分割，是验证码识别中的难点。针对由扭曲粘连字符构成的验证码，提出一种基于密集尺度不变特征变换( DENSE SIFT)和随机抽样一致性算法( RANSAC)的识别方法。首先通过 DENSE SIFT 特征匹配获得匹配点集，再利用RANSAC算法获取匹配信息，最后采用队列式分析算法得出识别结果。实验表明，该方法对不同难度级别的扭曲粘连验证码均有较好的效果。