Recently, large-scale diffusion models, e.g., Stable diffusion and DallE2,
have shown remarkable results on image synthesis. On the other hand,
large-scale cross-modal pre-trained models (e.g., CLIP, ALIGN, and FILIP) are
competent for various downstream tasks by learning to align vision and language
embeddings. In this paper, we explore the possibility of jointly modeling
generation and discrimination. Specifically, we propose DiffDis to unify the
cross-modal generative and discriminative pretraining into one single framework
under the diffusion process. DiffDis first formulates the image-text
discriminative problem as a generative diffusion process of the text embedding
from the text encoder conditioned on the image. Then, we propose a novel
dual-stream network architecture, which fuses the noisy text embedding with the
knowledge of latent images from different scales for image-text discriminative
learning. Moreover, the generative and discriminative tasks can efficiently
share the image-branch network structure in the multi-modality model.
Benefiting from diffusion-based unified training, DiffDis achieves both better
generation ability and cross-modal semantic alignment in one architecture.
Experimental results show that DiffDis outperforms single-task models on both
the image generation and the image-text discriminative tasks, e.g., 1.65%
improvement on average accuracy of zero-shot classification over 12 datasets
and 2.42 improvement on FID of zero-shot image synthesis.

在这篇论文中，我们提出了 DiffDis，通过扩展扩散过程，将跨模态生成和辨别预训练统一到一个框架中。DiffDis 通过融合噪声文本嵌入和来自不同尺度的潜在图像的知识，提出了一种新颖的双流网络架构，来解决图像 - 文本辨别任务。通过基于扩散的统一训练，DiffDis 在一种体系结构中实现了更好的生成能力和跨模态语义对齐。实验结果表明，DiffDis 在图像生成和图像 - 文本辨别任务上优于单一任务模型，例如在 12 个数据集上的零样本分类的平均准确性提高了 1.65％，在零样本图像合成的 FID 上提高了 2.42 个点。