用感知监督提升像素扩散模型清晰度,生成更逼真图像。
PixelGen: Improving Pixel Diffusion with Perceptual Supervision
- 在像素空间直接生成图像,结合感知损失优化细节和语义。
- ImageNet-256上FID达5.11,优于传统潜空间扩散模型。
- 适合追求高质量生成且希望简化流程的研究者与开发者。
像素扩散直接在像素空间生成图像,避免了两阶段潜空间扩散中的VAE伪影和表征瓶颈。近期的JiT方法通过x-prediction简化了像素扩散,使模型预测干净图像而非速度。然而,标准的像素级扩散损失对所有像素同等对待,浪费模型容量于感知不重要的信号,常导致图像模糊。我们提出PixelGen,一个端到端的像素扩散框架,通过感知监督增强x-prediction。具体地,PixelGen在x-prediction基础上引入两种互补的感知损失:用于局部纹理的LPIPS损失和用于全局语义的P-DINO损失。为保持样本多样性,PixelGen还提出噪声门控策略,仅在低噪声时间步应用这些损失。在无分类器自由引导的情况下,PixelGen于ImageNet-256训练80轮后取得5.11的FID,超越潜空间扩散基线。此外,PixelGen可高效扩展至文生图任务,在8×H800 GPU上仅用6天训练即达到0.79的GenEval得分。结果表明,感知监督显著缩小了像素与潜空间扩散的差距,同时保留简洁的一阶段流程。代码已开源:https://github.com/Zehong-Ma/PixelGen。
原文摘要 · Abstract (English)
Pixel diffusion generates images directly in pixel space, avoiding the VAE artifacts and representational bottlenecks of two-stage latent diffusion. Recent JiT further simplifies pixel diffusion with x-prediction, where the model predicts clean images rather than velocity. However, the standard pixel-wise diffusion loss treats all pixels equally, spending model capacity to perceptually insignificant signals and often leading to blurry samples. We propose PixelGen, an end-to-end pixel diffusion framework that augments x-prediction with perceptual supervision. Specifically, PixelGen introduces two complementary perceptual losses on top of x-prediction: an LPIPS loss for local textures and a P-DINO loss for global semantics. To preserve sample coverage, PixelGen further proposes a noise-gating strategy that applies these losses only at lower-noise timesteps. On ImageNet-256 without classifier-free guidance, PixelGen achieves an FID of 5.11 in 80 training epochs, surpassing the latent diffusion baselines. Moreover, PixelGen scales efficiently to text-to-image generation, reaching a GenEval score of 0.79 with only 6 days of training on 8xH800 GPUs. These results show that perceptual supervision substantially narrows the gap between pixel and latent diffusion while preserving a simple one-stage pipeline. Codes are available at https://github.com/Zehong-Ma/PixelGen.
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