AWP: Activation-based Window Pruning for Gigapixel Object Detection

Gigapixel object detection in High-Resolution Wide (HRW) images faces extreme spatial sparsity where targets often occupy less than 5% of the image area while computation is wasted on vast uninformative regions. Existing token selection methods require either complex evolutionary search or training additional learnable modules. We present AWP (Activation-based Window Pruning), which discovers that the mean of Feed-Forward Network (FFN) activations naturally encodes window importance, enabling parameter-free selection without additional modules. Leveraging this intrinsic signal, AWP performs window pruning with remarkable effectiveness. On the PANDA gigapixel dataset, AWP outperforms the previous state-of-the-art by +1.6% AP₅₀ with 26.2% FLOPs reduction, particularly excelling on small objects (+5.1% APₛ). When applied to Swin Transformer, AWP demonstrates strong generalization, retaining 97.4% of baseline performance with 50% windows pruned. Remarkably, AWP enables zero-shot application by directly replacing learned selection modules, improving baseline by +0.6% AP₅₀ without retraining. Our work reveals that window-based vision transformers inherently encode spatial importance through FFN activations, offering a simple yet powerful alternative to existing selection mechanisms, especially for High-Resolution Wide images.