Semi-Supervised Image Classification Based on Local and Global Regression

The insufficiency of labeled samples is a major problem in automatic image annotation. However, unlabeled samples are readily available and abundant. Hence, semi-supervised learning methods, which utilize partly labeled samples and a large amount of unlabeled samples, have attracted increased attention in the field of image classification. During the past decade, graph-based semi-supervised learning became one of the most important research areas in semi-supervised learning. In this letter, we propose a novel and effective graph based semi-supervised learning method for image classification. The new method is based on local and global regression regularization. The local regression regularization adopts a set of local classification functions to preserve both local discriminative and geometrical information; while the global regression regularization preserves the global discriminative information and calculates the projection matrix for out-of-sample extrapolation. Extensive simulations based on synthetic and real-world datasets verify the effectiveness of the proposed method.