Abstract:To address the challenge of managing mis-shelved books during the intelligent transformation of university libraries, this paper proposes a spatial–frequency dual-domain collaborative detection method based on wavelet transform. The method incorporates a multi-scale spatial-frequency dynamic fusion module, in which Haar wavelet decomposition is employed to downsample and extract geometric deformation features of book spines, while inverse wavelet transform is used to reconstruct global texture distribution. This design fully leverages the complementary advantages of spatial and frequency domain information, achieving deep fusion of multi-scale features. To enhance the joint training of classification and localization, a match-aware loss function is introduced to optimize feature matching quality. For text regions susceptible to illumination variations and complex background interference, a morphological–PMD diffusion collaborative preprocessing pipeline is developed, integrating adaptive gamma correction with dynamic structural element closing operations, thereby significantly improving text-region robustness. Experimental results demonstrate that in complex scenarios such as densely arranged books the proposed method achieves average precision metrics of mAP@0.5:0.95, mAP@0.75, and mAR@0.5:0.95 at 80.2%, 96.8%, and 88.6%, respectively, providing reliable technical support for intelligent bookshelf management systems.