Semantically-enhanced kernel canonical correlation analysis: a multi-label cross-modal retrieval

Aiming at measuring the inter-media semantic similarities, cross-modal retrieval tries to align heterogenous features to an intermediate common subspace in which they can be reasonably compared. This is based on the same understanding of the semantics which are represented by different modalities. However, the semantics can usually be reflected by multiple concepts since concepts co-occur in real-world rather than occur in isolation. This leads to a more challenging task of multi-label cross-modal retrieval in which multiple concepts are annotated as labels for images as an example. More importantly, the co-occurrence patterns of concepts result in correlated pairs of labels whose relationships need to be considered in an accurate cross-modal retrieval. In this paper, we propose multi-label kernel canonical correlation analysis (ml-KCCA), a novel approach for cross-modal retrieval which enhances kernel CCA with high-level semantic information reflected in multi-label annotations. By kernelizing correlation extraction from multi-label information, more complex non-linear correlations between different modalities can be measured in order to learn a discriminative subspace which is more suitable for cross-modal retrieval tasks. Extensive evaluations on public datasets have validated the improvements of our approach over the state-of-the-art cross-modal retrieval approaches including other CCA extensions.