Text-conditional image synthesis is one of the most commonly used techniques for creative content generation that follows human’s fabulous imaginations through free-form languages.

We assess text-conditional image synthesis on the MS-COCO validation set (Lin et al., 2014) and LN-COCO, the COCO subset of Localized Narratives (PontTuset et al., 2020), following prior works (Xu et al., 2018; Yu et al., 2022b). The MS-COCO dataset primarily contains high-level image abstractions with shorter captions, whereas LN-COCO provides more comprehensive image descriptions (Yu et al., 2022b). DREAMLLM samples 8 images per text prompt on MSCOCO by CLIP score ranking, following previous works (Ramesh et al., 2022). On LN-COCO, DREAMLLM samples one image per prompt without CLIP ranking since the text is too long and exceeds the CLIP length limit. Note that Parti samples 16 images per prompt with CoCa (Yu et al., 2022a). Our evaluation metric is the zero-shot Fréchet Inception Distance (FID) (Heusel et al., 2017), the results of which are presented in Table 2. We note three key observations: i) Our DREAMLLM shows a significant FID improvement over the Stable Diffusion baseline after stage-I alignment, reducing the score by 3.67 and 11.83 on MS-COCO and LN-COCO respectively. Further, FID improvements of 3.97 and 13.73 are achieved after pretraining and supervised fine-tuning. The substantial improvement on LN-COCO underscores DREAMLLM’s superior capability in processing long-context information. ii) When compared to prior specialist models, DREAMLLM delivers competitive results based on the SD image decoder. iii) DREAMLLM consistently outperforms concurrent MLLMs-based image synthesis methods. For instance, DREAMLLM-7B surpasses Emu-13B by a significant 3.20 FID on MS-COCO. See qualitative results on text-to-image synthesis in Fig. 10 and Fig. 11 in Appendix B.