Alleviating Distortion in Image Generation via Multi-Resolution Diffusion Models

Qihao Liu 1,2* Zhanpeng Zeng 1,3* Ju He 1,2* Qihang Yu 1 Xiaohui Shen 1 Liang-Chieh Chen 1

 1 ByteDance  2 Johns Hopkins University  3 University of Wisconsin-Madison
 * equal contribution
[Paper]  [Code (coming soon)]  [BibTeX]
 
 
We propose DiMR, a new diffusion backbone that achieves state-of-the-art image generation.
 
 
 

Highlights

 

  • [SOTA image generation] On the ImageNet 256 x 256 benchmark, DiMR with only 505M parameters surpasses all existing image generation models of various sizes, without any bells and whistles.
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  • [Alleviating Distortions] With the proposed Multi-Resolution Network, DiMR alleviates distortions and enhances visual fidelity without increasing computational costs.
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    In this figure, we randomly visualize the detected low-fidelity images, identified by a pretrained classifier, which are generated by the best models from the baselines and our DiMR.
     
     

    Abstract

     

    This paper presents innovative enhancements to diffusion models by integrating a novel multi-resolution network and time-dependent layer normalization. Diffusion models have gained prominence for their effectiveness in high-fidelity image generation. While conventional approaches rely on convolutional U-Net architectures, recent Transformer-based designs have demonstrated superior performance and scalability. However, Transformer architectures, which tokenize input data (via "patchification"), face a trade-off between visual fidelity and computational complexity due to the quadratic nature of self-attention operations concerning token length. While larger patch sizes enable attention computation efficiency, they struggle to capture fine-grained visual details, leading to image distortions. To address this challenge, we propose augmenting the Diffusion model with the Multi-Resolution network (DiMR), a framework that refines features across multiple resolutions, progressively enhancing detail from low to high resolution. Additionally, we introduce Time-Dependent Layer Normalization (TD-LN), a parameter-efficient approach that incorporates time-dependent parameters into layer normalization to inject time information and achieve superior performance. Our method's efficacy is demonstrated on the class-conditional ImageNet generation benchmark, where DiMR-XL variants outperform prior diffusion models, setting new state-of-the-art FID scores of 1.70 on ImageNet 256 x 256 and 2.89 on ImageNet 512 x 512.

     

     
     

    Multi-Resolution Network

     

     

    We propose DiMR that enhances Diffusion models with a Multi-Resolution Network. In the figure, we present the Multi-Resolution Network with three branches. The first branch processes the lowest resolution (4 times smaller than the input size) using powerful Transformer blocks, while the other two branches handle higher resolutions (2 times smaller than the input size and the same size as the input, respectively) using effective ConvNeXt blocks. The network employs a feature cascade framework, progressively upsampling lower-resolution features to higher resolutions to reduce distortion in image generation. The Transformer and ConvNeXt blocks are further enhanced by the proposed Time-Dependent Layer Normalization (TD-LN).

     

     

    Time-Dependent Layer Normalization

     

    We conducted Principal Component Analysis on the learned scale (γ1, γ2) and shift (β1, β2) parameters from a parameter-heavy MLP in the adaLN-Zero module of a pre-trained DiT-XL/2 model. We observed that the learned parameters can be largely explained by two principal components, suggesting that a parameter-heavy MLP might be unnecessary and that a simpler function could suffice.

    We replaced the MLP in adaLN-Zero with learnable parameters p1, p2, p3, and p4, estimating the scale and shift parameters through the linear interpolation of p1 with p2, and p3 with p4, respectively.

     

     

    Main Experimental Results

     

     

     

    Bibtex

    @article{liu2024alleviating,
  title={Alleviating Distortion in Image Generation via Multi-Resolution Diffusion Models},
  author={Liu, Qihao and Zeng, Zhanpeng and He, Ju and Yu, Qihang and Shen, Xiaohui and Chen, Liang-Chieh},
  journal={arXiv preprint arXiv:2406.09416},
  year={2024}
}