论文标题

双向特征重建网络,用于细粒度的几片图像分类

Bi-directional Feature Reconstruction Network for Fine-Grained Few-Shot Image Classification

论文作者

Wu, Jijie, Chang, Dongliang, Sain, Aneeshan, Li, Xiaoxu, Ma, Zhanyu, Cao, Jie, Guo, Jun, Song, Yi-Zhe

论文摘要

细颗粒的几片图像分类的主要挑战是学习具有较高级别和较低阶层内变化的特征表示,只有很少的标签样品。然而,对于这种细粒度的环境,常规的几次学习方法不能天真地采用 - 快速的试点研究表明,它们实际上推动了相反的情况(即,较低的阶层变化和较高的阶层内变化)。为了减轻此问题,先前的工作主要使用支持集来重建查询图像,然后利用公制学习来确定其类别。经过仔细的检查,我们进一步揭示了这种单向重建方法仅有助于增加类间变化,并且无效地应对类内变化。在本文中,我们首次引入了一种双重重建机制,该机制可以同时适应阶层间和阶层的变化。除了使用支持集重建以增加类间变化的查询集外,我们还进一步使用查询集来重建用于减少类内部变化的支持集。该设计有效地有助于模型探索更微妙和歧视性的特征,这对于手头的细粒度问题是关键。此外,我们还构建了一个自我重建模块,以与双向模块一起工作,以使功能更加歧视。与其他方法相比,三个广泛使用的细粒图像分类数据集的实验结果始终显示出很大的改进。代码可在以下网址提供:https://github.com/pris-cv/bi-frn。

The main challenge for fine-grained few-shot image classification is to learn feature representations with higher inter-class and lower intra-class variations, with a mere few labelled samples. Conventional few-shot learning methods however cannot be naively adopted for this fine-grained setting -- a quick pilot study reveals that they in fact push for the opposite (i.e., lower inter-class variations and higher intra-class variations). To alleviate this problem, prior works predominately use a support set to reconstruct the query image and then utilize metric learning to determine its category. Upon careful inspection, we further reveal that such unidirectional reconstruction methods only help to increase inter-class variations and are not effective in tackling intra-class variations. In this paper, we for the first time introduce a bi-reconstruction mechanism that can simultaneously accommodate for inter-class and intra-class variations. In addition to using the support set to reconstruct the query set for increasing inter-class variations, we further use the query set to reconstruct the support set for reducing intra-class variations. This design effectively helps the model to explore more subtle and discriminative features which is key for the fine-grained problem in hand. Furthermore, we also construct a self-reconstruction module to work alongside the bi-directional module to make the features even more discriminative. Experimental results on three widely used fine-grained image classification datasets consistently show considerable improvements compared with other methods. Codes are available at: https://github.com/PRIS-CV/Bi-FRN.

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