Improving Long-Text Alignment for Text-to-Image Diffusion Models

This repo is the official PyTorch implementation for Improving Long-Text Alignment for Text-to-Image Diffusion Models (LongAlign)

by Luping Liu^1,2, Chao Du², Tianyu Pang², Zehan Wang^2,4, Chongxuan Li³, Dong Xu¹.

¹The University of Hong Kong; ²Sea AI Lab, Singapore; ³Renmin University of China; ⁴Zhejiang University

What does this work do?

To improve long-text alignment for T2I diffusion models, we propose LongAlign, which features a segment-level encoding method for processing long texts and a decomposed preference optimization method for effective alignment training. For decomposed preference optimization, we find the preference models can be decomposed into two components: a text-relevant part and a text-irrelevant part. We propose a reweighting strategy that assigns different weights to these two components, reducing overfitting and enhancing alignment.

CLIP-based preference decomposition

• (a) Schematic results for text embeddings. (b) Statistics of the projection scalar $\eta$ for three CLIP-based preference models. (c) The relationship between the original preference score and the two scores after decomposition.

Generation result

• Generation results using our LongAlign and baselines. We highlight three key facts for each prompt and provide the evaluation results at the end.

• Generation results using different preference models, with and without our reweighting strategy.

How to run the code?

Prepare environment

pip install -r requirements.txt
# if you encounter an error with LoRA, please run `pip uninstall peft`

Prepare dataset and checkpoint

• 2 million long-text & image dataset (the raw images need to be downloaded separately): https://huggingface.co/datasets/luping-liu/LongAlign
• Stable Diffusion v1.5 (this will download automatically): https://huggingface.co/stable-diffusion-v1-5/stable-diffusion-v1-5
• T5-adapter (please download this to ./model/LaVi-Bridge): https://huggingface.co/shihaozhao/LaVi-Bridge/tree/main/t5_unet/adapter
• Denscore (this will download automatically): https://huggingface.co/luping-liu/Denscore
• longSD (please download this to ./model/longSD or train them yourself): https://huggingface.co/luping-liu/LongSD

Train original Stable Diffusion

# support long-text inputs
bash run_unet.sh align ct5f
# please move {args.output_dir}/s{global_step_}_lora_vis.pt --> {args.output_dir}/lora_vis.pt and so on

# preference optimization for long-text alignment
bash run_unet.sh reward test

Train LCM-version Stable Diffusion

# support LCM sampling
bash run_unet.sh lcm ct5f

# preference optimization for long-text alignment
bash run_unet.sh reward_lcm test

References

If you find this work useful for your research, please consider citing:

@article{liu2024improving,
      title={Improving Long-Text Alignment for Text-to-Image Diffusion Models}, 
      author={Luping Liu and Chao Du and Tianyu Pang and Zehan Wang and Chongxuan Li and Dong Xu},
      year={2024},
      journal={arXiv preprint arXiv:2410.11817},
}

This code is mainly built upon diffusers and LaVi-Bridge repositories, which you might also find interesting.