怎么生成透明背景的图片（PNG 抠图）？

{
  "model": "gpt-image-2",
  "prompt": "a cute cartoon fox sticker, clean cutout edges, no shadow",
  "background": "transparent",
  "output_format": "png"
}

curl https://api.apiyi.com/v1/images/generations \
  -H "Authorization: Bearer $APIYI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-image-2",
    "prompt": "a cute cartoon fox sticker, flat vector illustration, single centered subject, clean cutout edges, no background, no shadow",
    "background": "transparent",
    "output_format": "png",
    "quality": "low"
  }'

curl https://api.apiyi.com/v1/images/edits \
  -H "Authorization: Bearer $APIYI_API_KEY" \
  -F model=gpt-image-2 \
  -F [email protected] \
  -F 'prompt=remove the background completely and keep only the fox, clean cutout edges, no shadow' \
  -F background=transparent \
  -F output_format=png

{
  "model": "gpt-5.2",
  "input": "生成一个卡通狐狸贴纸",
  "tools": [{
    "type": "image_generation",
    "model": "gpt-image-2",
    "background": "transparent",
    "output_format": "png"
  }]
}

{
  "error": {
    "message": "Transparent background is not supported for JPEG output format",
    "param": "background",
    "code": "invalid_value"
  }
}