  In this paper, we introduce PixArt-\Sigma, a Diffusion Transformer
model~(DiT) capable of directly generating images at 4K resolution.
PixArt-\Sigma represents a significant advancement over its predecessor,
PixArt-\alpha, offering images of markedly higher fidelity and improved
alignment with text prompts. A key feature of PixArt-\Sigma is its training
efficiency. Leveraging the foundational pre-training of PixArt-\alpha, it
evolves from the `weaker' baseline to a `stronger' model via incorporating
higher quality data, a process we term "weak-to-strong training". The
advancements in PixArt-\Sigma are twofold: (1) High-Quality Training Data:
PixArt-\Sigma incorporates superior-quality image data, paired with more
precise and detailed image captions. (2) Efficient Token Compression: we
propose a novel attention module within the DiT framework that compresses both
keys and values, significantly improving efficiency and facilitating
ultra-high-resolution image generation. Thanks to these improvements,
PixArt-\Sigma achieves superior image quality and user prompt adherence
capabilities with significantly smaller model size (0.6B parameters) than
existing text-to-image diffusion models, such as SDXL (2.6B parameters) and SD
Cascade (5.1B parameters). Moreover, PixArt-\Sigma's capability to generate 4K
images supports the creation of high-resolution posters and wallpapers,
efficiently bolstering the production of high-quality visual content in
industries such as film and gaming.
