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Generate images from a user-provided prompt.

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Endpoint

POST https://api.stepfun.ai/v1/images/generations

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Request parameters

  • model string required
    The model name to use. Currently supported:
    • step-image-edit-2
  • prompt string required
    Text description of the image. Maximum length: 512 characters.
  • size string optional
    The size of the generated image. Default 1024x1024.
    • step-image-edit-2 (format is height x width, not width x height):
      • Square: 1024x1024
      • Rectangular: 768x1360, 896x1184, 1360x768, 1184x896
  • n int optional
    Number of images to generate. Currently only one image per request is supported.
  • response_format string optional
    Format of the returned image. Supported: b64_json or url. Default url.
  • seed int optional
    Random seed.
    • step-image-edit-2: range [0, 2147483647]. If not provided, the server randomly generates a seed.
  • steps int optional
    Number of generation steps.
    • step-image-edit-2: range [1, 50]. Default 8.
  • cfg_scale float optional
    Classifier-free guidance scale.
    • step-image-edit-2: must be >= 1.0, range [1.0, 10.0]. Default 1.0.
  • negative_prompt string optional
    Negative prompt. Up to 512 characters, default "". When cfg_scale = 1.0, the current implementation does not pass the negative prompt to the underlying model.
  • text_mode bool optional
    Optimization strategy for text-rendering scenarios. Default False, enable as needed.

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Response

  • created int
    Timestamp of when the image was created (seconds).
  • data object array
    Array of generated image objects.
    • seed int
      The seed used during generation. Same seeds produce similar images.
    • finish_reason string
      Reason for completion. success indicates successful generation; content_filtered indicates successful generation but stopped due to content filtering.
    • b64_json string
      Base64-encoded image. Returned when response_format is b64_json.
    • url string
      Image download URL. Returned when response_format is url. The URL has a limited validity period (currently 2 hours); download and save the image to your own storage to avoid relying on this link.
{
  "created": 1589478378,
  "data": [
    {
      "b64_json": "AAAAIGZ0eXBpc29tAAACAGlzb21pc28yYXZjMW1",
      "finish_reason": "success",
      "seed": 123838
    }
  ]
}

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Example

curl https://api.stepfun.ai/v1/images/generations \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $STEP_API_KEY" \
  -d '{
    "model": "step-image-edit-2",
    "prompt": "A serene alpine lake at sunset, mirror reflection, photorealistic",
    "response_format": "b64_json",
    "cfg_scale": 1.0,
    "steps": 8,
    "seed": 1,
    "text_mode": true
  }'