Contrastive models like CLIP have been shown to learn robust representations of images that capture both semantics and style. To leverage these representations for image generation, we propose a two-stage model: a prior that generates a CLIP image embedding given a text caption, and a decoder that generates an image conditioned on the image embedding. We show that explicitly generating image representations improves image diversity with minimal loss in photorealism and caption similarity. Our decoders conditioned on image representations can also produce variations of an image that preserve both its semantics and style, while varying the non-essential details absent from the image representation. Moreover, the joint embedding space of CLIP enables language-guided image manipulations in a zero-shot fashion. We use diffusion models for the decoder and experiment with both autoregressive and diffusion models for the prior, finding that the latter are computationally more efficient and produce higher-quality samples.

提出一个两阶段模型，先用 prior 生成 CLIP 图像嵌入，再由 decoder 在图像嵌入的条件下生成图像。实验表明该模型可以提高图像的多样性，并在完美保留语义和风格前提下变化非必要的细节。利用扩散模型作为decoder,同时使用自回归和扩散模型作为prior，发现后者更加高效且产生的样本更优。

使用CLIP潜变量的分层文本条件图像生成