Image Compression and Output Resolution
Resolution is determined by the model name
4ALL API image resolution is selected via the model suffix; do not rely on the size parameter:
| Suffix | Description |
|---|---|
| None | Standard resolution (about 1K) |
-2k | 2K high definition |
-4k | 4K ultra-high definition (GPT-Image series) |
Use this in combination with the aspect-ratio suffix, such as gpt-image-2-portrait-2k and gemini-3.1-flash-image-square-2k.
For the full rules, see Image and Video Generation Models.
How to choose a tier
- Web/social media display: the standard tier is enough; it loads fast and costs less;
- Printing / enlarged crops / main product images for e-commerce: start at 2K;
- Finished assets that need post-processing: 4K, but both unit cost and processing time increase significantly;
- It is recommended to iterate on prompts with the standard tier until satisfactory, then generate the final result in high resolution—avoid repeated trial and error at 4K.
Output format and size
- When a URL is returned, download the original image directly; when base64 is returned, note that the response body is large (4K can reach several MB), so the client and proxy body size limits should be increased;
- After obtaining the original image, compress and generate multiple specs on your own (webp/avif + thumbnails) before uploading to the CDN; do not send the original image directly to the frontend;
- Generated image URLs are time-limited, so be sure to transfer them to your own object storage first.
Common issues
- Blurry images: most likely the standard tier is being upscaled on the frontend; switch to the 2K/4K tier;
- Gray edges on white-background images: specify in the prompt “pure white background #FFFFFF, no shadows”;
- File size too large: converting to webp on the server side (quality 80) can usually reduce size by 60–80% with no visible loss.