Solving Diffusion ODEs with Optimal Boundary Conditions for Better Image Super-Resolution
ICLR 2024(2023)
摘要
Diffusion models, as a kind of powerful generative model, have given
impressive results on image super-resolution (SR) tasks. However, due to the
randomness introduced in the reverse process of diffusion models, the
performances of diffusion-based SR models are fluctuating at every time of
sampling, especially for samplers with few resampled steps. This inherent
randomness of diffusion models results in ineffectiveness and instability,
making it challenging for users to guarantee the quality of SR results.
However, our work takes this randomness as an opportunity: fully analyzing and
leveraging it leads to the construction of an effective plug-and-play sampling
method that owns the potential to benefit a series of diffusion-based SR
methods. More in detail, we propose to steadily sample high-quality SR images
from pre-trained diffusion-based SR models by solving diffusion ordinary
differential equations (diffusion ODEs) with optimal boundary conditions (BCs)
and analyze the characteristics between the choices of BCs and their
corresponding SR results. Our analysis shows the route to obtain an
approximately optimal BC via an efficient exploration in the whole space. The
quality of SR results sampled by the proposed method with fewer steps
outperforms the quality of results sampled by current methods with randomness
from the same pre-trained diffusion-based SR model, which means that our
sampling method "boosts" current diffusion-based SR models without any
additional training.
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关键词
diffusion models,diffusion ODE,image super-resolution
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