Label-Efficient Hyperspectral Image Classification via Spectral FiLM Modulation of Low-Level Pretrained Diffusion Features

Hyperspectral imaging (HSI) enables detailed land cover classification, but low spatial resolution and sparse annotations pose significant challenges. We present a label-efficient framework that leverages spatial features from a frozen diffusion model pretrained on natural images. Specifically, we extract low-level representations from high-resolution decoder layers at early denoising timesteps, which transfer well to the low-texture setting of HSI. To combine spectral and spatial information, we introduce a lightweight FiLM-based fusion module that adaptively integrates spectral cues into frozen spatial features, enabling effective multimodal learning under sparse supervision. Experiments on two recent hyperspectral datasets show that our method outperforms state-of-the-art approaches using only the sparse training labels provided. Ablation studies further validate the benefit of diffusion-based features and spectral-aware fusion. Our results suggest that pretrained diffusion models can support domain-agnostic, label-efficient representation learning in remote sensing and scientific imaging tasks.