Think-Then-Generate: Reasoning-Aware Text-to-Image Diffusion with LLM Encoders

TL;DR

This paper introduces a reasoning-aware text-to-image diffusion framework that leverages LLMs for prompt rewriting and reasoning, significantly improving semantic accuracy and visual realism in generated images.

Contribution

It proposes the think-then-generate paradigm, enabling LLMs to reason about prompts before image synthesis, and introduces co-optimization with diffusion models for enhanced semantic fidelity.

Findings

Improved factual consistency and semantic alignment in generated images.

Achieved a WISE score of 0.79, close to GPT-4 performance.

Enhanced image editing capabilities with reasoning-aware prompts.

Abstract

Recent progress in text-to-image (T2I) diffusion models (DMs) has enabled high-quality visual synthesis from diverse textual prompts. Yet, most existing T2I DMs, even those equipped with large language model (LLM)-based text encoders, remain text-pixel mappers -- they employ LLMs merely as text encoders, without leveraging their inherent reasoning capabilities to infer what should be visually depicted given the textual prompt. To move beyond such literal generation, we propose the think-then-generate (T2G) paradigm, where the LLM-based text encoder is encouraged to reason about and rewrite raw user prompts; the states of the rewritten prompts then serve as diffusion conditioning. To achieve this, we first activate the think-then-rewrite pattern of the LLM encoder with a lightweight supervised fine-tuning process. Subsequently, the LLM encoder and diffusion backbone are co-optimized to ensure faithful reasoning about the context and accurate rendering of the semantics via Dual-GRPO. In particular, the text encoder is reinforced using image-grounded rewards to infer and recall world knowledge, while the diffusion backbone is pushed to produce semantically consistent and visually coherent images. Experiments show substantial improvements in factual consistency, semantic alignment, and visual realism across reasoning-based image generation and editing benchmarks, achieving 0.79 on WISE score, nearly on par with GPT-4. Our results constitute a promising step toward next-generation unified models with reasoning, expression, and demonstration capacities.