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Investigating Permutation-Invariant Discrete Representation Learning for Spatially Aligned Images

Jamie Stirling, Noura Al Moubayed and Hubert P. H. Shum
Proceedings of the 2026 International Conference on Pattern Recognition (ICPR), 2026

H5-Index: 68#

Investigating Permutation-Invariant Discrete Representation Learning for Spatially Aligned Images
# According to Google Scholar 2026

Abstract

Vector quantization approaches (VQ-VAE, VQ-GAN) learn discrete neural representations of images, but these representations are inherently position-dependent: codes are spatially arranged and contextually entangled, requiring autoregressive or diffusion-based priors to model their dependencies at sample time. In this work, we ask whether positional information is necessary for discrete representations of spatially aligned data. We propose the permutation-invariant vector-quantized autoencoder (PI-VQ), in which latent codes are constrained to carry no positional information. We find that this constraint encourages codes to capture global, semantic features, and enables direct interpolation between images without a learned prior. To address the reduced information capacity of permutation-invariant representations, we introduce matching quantization, a vector quantization algorithm based on optimal bipartite matching that increases effective bottleneck capacity by 3.5X relative to naive nearest-neighbour quantization. The compositional structure of the learned codes further enables interpolation-based sampling, allowing synthesis of novel images in a single forward pass. We evaluate PI-VQ on CelebA, CelebA-HQ and FFHQ, obtaining competitive precision, density and coverage metrics for images synthesised with our approach. We discuss the trade-offs inherent to position-free representations, including separability and interpretability of the latent codes, pointing to numerous directions for future work.


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Plain Text

Jamie Stirling, Noura Al Moubayed and Hubert P. H. Shum, "Investigating Permutation-Invariant Discrete Representation Learning for Spatially Aligned Images," in Proceedings of the 2026 International Conference on Pattern Recognition, Lyon, France, 2026.

BibTeX

@inproceedings{stirling26investigating,
 author={Stirling, Jamie and Moubayed, Noura Al and Shum, Hubert P. H.},
 booktitle={Proceedings of the 2026 International Conference on Pattern Recognition},
 title={Investigating Permutation-Invariant Discrete Representation Learning for Spatially Aligned Images},
 year={2026},
 location={Lyon, France},
}

RIS

TY  - CONF
AU  - Stirling, Jamie
AU  - Moubayed, Noura Al
AU  - Shum, Hubert P. H.
T2  - Proceedings of the 2026 International Conference on Pattern Recognition
TI  - Investigating Permutation-Invariant Discrete Representation Learning for Spatially Aligned Images
PY  - 2026
ER  - 


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