Weakly Supervised Image Classification with Coarse and Fine Labels

We consider image classification in a weakly supervised scenario where the training data are annotated at different levels of abstractions. A subset of the training data are annotated with coarse labels (e.g. wolf, dog), while the rest of the training data are annotated with fine labels (e.g. breeds of wolves and dogs). Each coarse label corresponds to a superclass of several fine labels. Our goal is to learn a model that can classify a new image into one of the fine classes. We investigate how the coarsely labeled data can help improve the fine label classification. Since it is usually much easier to collect data with coarse labels than those with fine labels, the problem setup considered in this paper can benefit a wide range of real-world applications. We propose a model based on convolutional neural networks (CNNs) to address this problem. We demonstrate the effectiveness of the proposed model on several benchmark datasets. Our model significantly outperforms the naive approach that discards the extra coarsely labeled data.