User-Click-Data-Based Fine-Grained Image Recognition via Weakly Supervised Metric Learning

We present a novel fine-grained image recognition framework using user click data, which can bridge the semantic gap in distinguishing categories that are similar in visual. As query set in click data is usually large-scale and redundant, we first propose a click-feature-based query-merging approach to merge queries with similar semantics and construct a compact click feature. Afterward, we utilize this compact click feature and convolutional neural network (CNN)-based deep visual feature to jointly represent an image. Finally, with the combined feature, we employ the metriclearning-based template-matching scheme for efficient recognition. Considering the heavy noise in the training data, we introduce a reliability variable to characterize the image reliability, and propose a weakly-supervised metric and template leaning with smooth assumption and click prior (WMTLSC) method to jointly learn the distance metric, object templates, and image reliability. Extensive experiments are conducted on a public Clickture-Dog dataset and our newly established Clickture-Bird dataset. It is shown that the click-data-based query merging helps generating a highly compact (the dimension is reduced to 0.9%) and dense click feature for images, which greatly improves the computational efficiency. Also, introducing this click feature into CNN feature further boosts the recognition accuracy. The proposed framework performs much better than previous state-of-the-arts in fine-grained recognition tasks.