Concept model-based unsupervised web image re-ranking

Current large scale image retrieval engines rely heavily on the surrounding text information, which inevitably includes some irrelevant images in the retrieval results due to the noisy environment. To improve the retrieval performance, we propose an unsupervised web image re-ranking method by incorporating images´ visual information. Our method can automatically select a set of representative images from the original image pool as concept model, which is highly related to the query concept and critically important for the re-ranking result. With a similarity graph constructed by top results given by text based retrieval, we utilize Normalized Cut to select the part with the highest similarity density as concept model. We re-rank the rest images according to their similarities to the concept model. The advantages of our method are (i): Our method is unsupervised, and it doesn´t need any pre-prepared query/training image or user´s feedback, Thus it greatly facilitates users´ retrieval. (ii): By finding a set of images rather than single image, we are able to give a more complete and more robust model for the query concept. (iii): Multi-ranking Integration Strategy is adopted to re-rank the rest images. Experiments show that our method can achieve satisfying results.