Cross-Domain Image Classification in Complex Real-World Scenarios: With Test-Time Label or Continual Domain Shift

Publication Type:
Thesis
Issue Date:
2025
Full metadata record
Cross-domain image classification is proposed to address the distribution discrepancy between the source and target domains, commonly referred to as the domain gap. Although it has been proven effective in mitigating the domain gap between the source and target domains, cross-domain image classification still faces significant challenges in complex real-world scenarios. In this thesis, two specific challenges that commonly happen, namely, label shift and continual domain shift, for cross-domain image classification are investigated and addressed. For the label shift, this thesis focuses on cross-domain few-shot image classification (CDFSIC). A novel prompt-to-disentangle method is proposed to combine the benefits of domain generalisation and adaptation by disentangling source and target knowledge. For the continual domain shift, this thesis focuses on continual test-time adaptation (CoTTA). Based on the findings in CDFSIC, we design a similar strategy called the Source and Target Disentangle Transformer to explicitly disentangle source and target knowledge, thereby facilitating both the preservation of source knowledge and the extraction of target knowledge. Then, based on the observation that the recent CoTTA method is unstable in a small-batch setting, a novel task named single-sample CoTTA is proposed. A novel strategy, named effective buffer and resetting, is designed to increase adaptation stability. Moreover, we apply this method to zero-shot models, solving the label shift and continual domain shift simultaneously. Finally, we highlighted several future directions, including active CoTTA to address larger domain gaps with human calibrations and zero-shot CoTTA to tackle both label shift and continual domain shift.
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