International Journal of Engineering and Technology

Image Processing is an emerging research domain in every walk of data in our life. As a part image retrieval and its analysis have its significance in identifying and measuring different factors in different images. In this research work, we have analyzed the semantic gap factors in different image based CAPTCHAs to define relation between usability issues and semantic gap. Different techniques have been literature reviewed in which a number of methods for measuring the semantic gap has been proposed. For evaluation different image based CAPTCHAs are considered to deal with. We shall also provide a designing factor requirement for the CAPTCHA designers as the prime objective of CAPTCHA includes robustness along with usability.