这篇论文教你直接用文生图模型的内部表征来当奖励模型，效果比HPSv3好，还能加速推理，适合想搞图像生成优化的朋友
DiT-Reward利用预训练的文生图Diffusion Transformer（DiT）的生成表征进行奖励预测。在HPDv2和HPDv3基准上分别达到85.6%和77.6%的准确率，全面超越HPSv3。冻结生成骨干网络时，轻量头仍能提取有效偏好。用于优化Stable Diffusion 3.5 Large时，DiT-Reward在生成逼真度上明显优于HPSv3，且推理速度提升1.65倍。
DiT-Reward: Generative Representations for Text-to-Image Reward Modeling
Can representations learned for image generation also support the evaluation of generated images? We study text-to-image reward prediction as a downstream task of generative representation learning. To this end, we introduce DiT-Reward, which converts a pretrained text-to-image Diffusion Transformer into a reward model by processing near-clean image latents and aggregating text-conditioned image representations across transformer layers. Under the same training data mixture as HPSv3, DiT-Reward outperforms HPSv3 on all four evaluated preference benchmarks, reaching 85.6% on HPDv2 and 77.6% on HPDv3. When the generative backbone is frozen, a lightweight learned head can still extract meaningful preference predictions from its representations. Probing across depth further reveals that downstream reward performance is strongest in the middle-to-late layers and benefits from combining representations across different stages. We also observe consistent positive scaling with generative backbone capacity. Finally, when used to optimize Stable Diffusion 3.5 Large with Flow-GRPO, DiT-Reward outperforms HPSv3 along the matched training trajectory, with particularly clear gains in realism. Direct latent scoring also achieves a 1.65x inference speedup over HPSv3 with comparable peak memory. These results show that pretrained generative DiTs provide transferable representations for reward modeling and policy optimization.