VOSR: A Vision-Only Generative Model for Image Super-Resolution

TL;DR

VOSR introduces a vision-only generative model for image super-resolution that rivals text-to-image diffusion models, achieving high quality with less training cost and no multimodal pretraining.

Contribution

The paper presents VOSR, a purely visual data-trained super-resolution model that outperforms T2I-based methods in quality and efficiency, with a novel guidance strategy.

Findings

VOSR achieves competitive or better perceptual quality than T2I-based methods.

VOSR requires less than one-tenth of the training cost of comparable methods.

VOSR produces more faithful structures with fewer hallucinations.

Abstract

Most of the recent generative image super-resolution (SR) methods rely on adapting large text-to-image (T2I) diffusion models pretrained on web-scale text-image data. While effective, this paradigm starts from a generic T2I generator, despite that SR is fundamentally a low-resolution (LR) input-conditioned image restoration task. In this work, we investigate whether an SR model trained purely on visual data can rival T2I-based ones. To this end, we propose VOSR, a Vision-Only generative framework for SR. We first extract semantically rich and spatially grounded features from the LR input using a pretrained vision encoder as visual semantic guidance. We then revisit classifier-free guidance for training generative models and show that the standard unconditional branch is ill-suited to restoration models trained from scratch. We therefore replace it with a restoration-oriented guidance strategy that preserves weak LR anchors. Built upon these designs, we first train a multi-step VOSR model from scratch and then distill it into a one-step model for efficient inference. VOSR requires less than one-tenth of the training cost of representative T2I-based SR methods, yet in both multi-step and one-step settings, it achieves competitive or even better perceptual quality and efficiency, while producing more faithful structures with fewer hallucinations on both synthetic and real-world benchmarks. Our results, for the first time, show that high-quality generative SR can be achieved without multimodal pretraining. The code and models can be found at https://github.com/cswry/VOSR.