Digital photography technologies permit quick and easy uploading of any image to the web. Millions of images being are uploaded on the World Wide Web every day by a wide range of users. Most of the uploaded images are not readily accessible as they are not organized so as to allow efficient searching, retrieval, and ultimately browsing. Currently major commercial search engines utilize a process known as Annotation Based Image Retrieval (ABIR) to execute search requests focused on retrieving an image. Even though the information sought is an image, the ABIR technique primarily relies on textual information associated with an image to complete the search and retrieval process.
For the first phase of the study, using the game of cricket as the domain, this research compared the performance of three commonly used search engines for image retrieval: Google, Yahoo and MSN Live. Factors used for the evaluation of these search engines include query types, number of images retrieved, and the type of search engine. Results of the empirical evaluation show that while the Google search engine performed better than Yahoo and MSN Live in situations where there is no refiner, the performance of all three search engines dropped drastically when a refiner was added. The other methodology to search for images is Content Based Image Retrieval (CBIR) which searches for the images based on the image features such as color, texture, and shape is still at a nascent stage and has not been incorporated in the commercial search engines. The image features are at a low level compared to the high level textual features. The gap between the low level image features and the high level textual features is termed as Semantic Gap. Semantic gap has been the factor that limits the Content Based algorithms to perform effectively.
This research addresses the issue of the image retrieval problem by systematically coupling the ABIR and the CBIR algorithms and uses the human input wherever needed to reduce the semantic gap. The key research question addressed by this study is whether a human integrated approach helps in better image retrieval. In this research, a systematic study to identify the role of human annotation in the search and retrieval of images was performed. Results showed that as long as a subject matter expert is annotating the image, there was no variability in the performance of search engines, in measures of precision and recall.
Moreover, empirical results suggested that the human integrated approach results in a better performance when compared to the pure Annotation Based Image Retrieval or the Content Based Image Retrieval. Further research can be developed to slowly replace some aspects of the human input with machine learning algorithms.
One of the primary contributions of the framework was to demonstrate a novel framework which systematically reduces the semantic gap by using the human input, the ABIR and the CBIR algorithms. Some of the other contributions include a methodology for systematically evaluating the effectiveness of the image search engines, and a methodology for using both generic and domain specific templates for the ABIR and the CBIR algorithms.