Ranking-Preserving Low-Rank Factorization for Image Annotation With Missing Labels

Abstract

Automatic image annotation has been extensively studied in the recent decades. Nevertheless, existing methods usually assume a properly labeled training set, which greatly inhibits their application to real-world datasets with incomplete labels. Due to their lack of special treatments for noisy data, most existing methods simply consider the missing labels as strictly negative ones, leading to the degradation of tagging accuracy. In light of such challenges, we propose a novel model in this paper, called ranking-preserving low-rank factorization. Specifically, we construct a local training set for each test image, and conduct low-rank matrix factorization on the model coefficient matrix, to simultaneously capture the label dependency and reduce the model complexity. Furthermore, to alleviate the ambiguity introduced by missing labels, the prediction model is learnt via tag ranking regularized by sample similarities and tag correlations, and both regularization terms are incorporated into our factorization scheme. By assembling all the aforementioned components together, our method obviates the need for making binary decisions based on unreliable data, and thus is more robust towards missing labels. Extensive empirical evaluations conducted on four datasets demonstrate the effectiveness of the proposed method.