  Recent text-to-image (T2I) generation models have demonstrated impressive
capabilities in creating images from text descriptions. However, these T2I
generation models often fall short of generating images that precisely match
the details of the text inputs, such as incorrect spatial relationship or
missing objects. In this paper, we introduce SELMA: Skill-Specific Expert
Learning and Merging with Auto-Generated Data, a novel paradigm to improve the
faithfulness of T2I models by fine-tuning models on automatically generated,
multi-skill image-text datasets, with skill-specific expert learning and
merging. First, SELMA leverages an LLM's in-context learning capability to
generate multiple datasets of text prompts that can teach different skills, and
then generates the images with a T2I model based on the prompts. Next, SELMA
adapts the T2I model to the new skills by learning multiple single-skill LoRA
(low-rank adaptation) experts followed by expert merging. Our independent
expert fine-tuning specializes multiple models for different skills, and expert
merging helps build a joint multi-skill T2I model that can generate faithful
images given diverse text prompts, while mitigating the knowledge conflict from
different datasets. We empirically demonstrate that SELMA significantly
improves the semantic alignment and text faithfulness of state-of-the-art T2I
diffusion models on multiple benchmarks (+2.1% on TIFA and +6.9% on DSG), human
preference metrics (PickScore, ImageReward, and HPS), as well as human
evaluation. Moreover, fine-tuning with image-text pairs auto-collected via
SELMA shows comparable performance to fine-tuning with ground truth data.
Lastly, we show that fine-tuning with images from a weaker T2I model can help
improve the generation quality of a stronger T2I model, suggesting promising
weak-to-strong generalization in T2I models.
