Abstract:Recently, food image recognition has received more and more attention for its wide applications in healthy diet management, smart restaurant, and so on. Unlike other object recognition tasks, food images belong to fine-grained ones with high intra-class variability and inter-class similarity. Furthermore, food images do not have fixed semantic patterns and specific spatial layout. These make food recognition more challenging. This study proposes a multi-scale jigsaw and reconstruction network (MJR-Net) for food recognition. MJR-Net is composed of three parts. The jigsaw and reconstruction module uses a method called destruction and reconstruction learning to destroy and reconstruct the original image to extract local discriminative details. Feature pyramid module can fuse mid-level features of different sizes to capture multi-scale local discriminative features. Channel-wise attention module can model the importance of different feature channels to enhance the discriminative visual patterns and weaken the noise patterns. The study also uses both A-softmax loss and Focal loss to optimize the network by increasing the inter-class variability and reweighting samples respectively. MJR-Net is evaluated on three food datasets (ETH Food-101, Vireo Food-172, and ISIA Food-500). The proposed method achieves 90.82%, 91.37%, and 64.95% accuracy, respectively. Experimental results show that, compared with other food recognition methods, MJR-Net shows greater competitiveness and especially achieves the state-of-the-art recognition performance on Vireo Food-172 and ISIA Food-500. Comprehensive ablation studies and visual analysis also prove the effectiveness of the proposed method.