Lossy Image Compression with Conditional Diffusion Models

Diffusion models are a new class of generative models that mark a milestone in high-quality image generation while relying on solid probabilistic principles. This makes them promising candidate models for neural image compression. This paper outlines an end-to-end optimized framework based on a conditional diffusion model for image compression. Besides latent variables inherent to the diffusion process, the model introduces an additional per-instance "content" latent variable to condition the denoising process. Upon decoding, the diffusion process conditionally generates/reconstructs an image using ancestral sampling. Our experiments show that this approach outperforms one of the best-performing conventional image codecs (BPG) and one neural codec on two compression benchmarks, where we focus on rate-perception tradeoffs. Qualitatively, our approach shows fewer decompression artifacts than the classical approach.