Transformer With Linear-Window Attention for Feature Matching

A transformer can capture long-term dependencies through an attention mechanism, and hence, can be applied to various vision tasks. However, its secondary computational complexity is a major obstacle in vision tasks that require accurate predictions. To address this limitation, this study introduces linear-window attention (LWA), a new attention model for a vision transformer. The transformer computes self-attention that is restricted to nonoverlapping local windows and represented as a linear dot product of kernel feature mappings. Furthermore, the computational complexity of each window is reduced to linear from quadratic using the constraint property of matrix products. In addition, we applied the LWA to feature matching to construct a coarse-to-fine-level detector-free feature matching method, called transformer with linear-window attention for feature matching TRLWAM. At the coarse level, we extracted the dense pixel-level matches, and at the fine level, we obtained the final matching results via multi-head multilayer perceptron refinement. We demonstrated the effectiveness of LWA through Replace experiments. The results showed that the TRLWAM could extract dense matches from low-texture or repetitive pattern regions in indoor environments, and exhibited excellent results with a low computational cost for MegaDepth and HPatches datasets. We believe the proposed LWA can provide new conceptions for transformer applications in visual tasks.