Data augmentation is a crucial technique for expanding training datasets, effectively alleviating the overfitting issue that arises from limited training data in deep learning models. This paper takes a fresh perspective and offers a scholarly exploration of image data augmentation, following a logical progression from unlearnable to learnable methods. The paper begins by providing a brief overview of the developmental history of data augmentation. It categorizes data augmentation techniques into unlearnable and learnable based on their “variation” strategies. Furthermore, the paper outlines the fundamental properties of data augmentation, including expansiveness, fidelity, generalizability, and self-adaptability. Subsequently, focusing on unlearnable and learnable data augmentation techniques, the paper further divides them into single-sample and multi-sample, global and local, image domain, and feature domain, categorically reviewing the basic principles and effects of various data augmentation methods based on the differences in the sources, scopes, and content of “variation” attributes. Ultimately, the comparative analysis of diverse data augmentation methodologies in specific tasks is conducted alongside a synthesis and projection of future research directions. By comprehensively analyzing diverse image data augmentation methods from a fresh perspective, this review reveals the intrinsic disparities between unlearnable and learnable data augmentation techniques. It paves the way for scholars to embark on innovative paths in data augmentation.
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