Zero-Shot Recognition with Guided Cropping

Pretrained vision-language models, e.g., CLIP, show promising zero-shot transfer capability across various unseen classification datasets. However, there is an inherent limitation: CLIP image encoders are typically designed to extract generic image-level features that summarize superfluous or confounding information for the target tasks. This results in degradation of classification performance, especially when objects of interest cover small areas of input images. In this work, we propose CLIP with Guided Cropping (GC-CLIP), where we use an off-the-shelf zero-shot object detection model in a preprocessing step to increase the focus of zero-shot classifiers on the object of interest and minimize the influence of extraneous image regions. We empirically show that our approach improves zero-shot performance across architectures and datasets, most favorably for small objects.