Knowledge distillation to effectively attain both region-of-interest and global semantics from an image where multiple objects appear

TL;DR

This paper introduces RveRNet, a novel architecture combining ROI and global context modules, enhanced by knowledge distillation from CNNs, to improve food image classification accuracy, especially for ambiguous cases.

Contribution

The paper proposes RveRNet, a new architecture that integrates ROI and global context modules, and demonstrates its effectiveness with knowledge distillation from CNNs for food classification.

Findings

RveRNet achieved a 10% higher F1 score than individual models.

Knowledge distillation from CNNs improved DeiT's robustness.

Global context modules enhanced classification of ambiguous images.

Abstract

Models based on convolutional neural networks (CNN) and transformers have steadily been improved. They also have been applied in various computer vision downstream tasks. However, in object detection tasks, accurately localizing and classifying almost infinite categories of foods in images remains challenging. To address these problems, we first segmented the food as the region-of-interest (ROI) by using the segment-anything model (SAM) and masked the rest of the region except ROI as black pixels. This process simplified the problems into a single classification for which annotation and training were much simpler than object detection. The images in which only the ROI was preserved were fed as inputs to fine-tune various off-the-shelf models that encoded their own inductive biases. Among them, Data-efficient image Transformers (DeiTs) had the best classification performance. Nonetheless, when foods' shapes and textures were similar, the contextual features of the ROI-only images were not enough for accurate classification. Therefore, we introduced a novel type of combined architecture, RveRNet, which consisted of ROI, extra-ROI, and integration modules that allowed it to account for both the ROI's and global contexts. The RveRNet's F1 score was 10% better than other individual models when classifying ambiguous food images. If the RveRNet's modules were DeiT with the knowledge distillation from the CNN, performed the best. We investigated how architectures can be made robust against input noise caused by permutation and translocation. The results indicated that there was a trade-off between how much the CNN teacher's knowledge could be distilled to DeiT and DeiT's innate strength. Code is publicly available at: https://github.com/Seonwhee-Genome/RveRNet.