X image ad specs: 1:1 or 1.91:1, 800px wide, 3 MB, from Sume

According to X's Creatives documentation, website and app-download image cards support 1:1 and 1.91:1, with a minimum width of 800px, a 3 MB file cap, and .bmp, .jpeg or .png files. Sume's Image API has 1:1 natively. For 1.91:1, request 2:1 and crop about 4.5% off the height.

Spec and the Sume route

Render 2:1 then crop and check

The script stops on a 202, asserts the width, saves a JPEG, and prints the byte size against the 3 MB cap. Use a model whose catalog lists 2:1; Ideogram 4.5 does.

import io, os, requests
from PIL import Image

API = "https://api.sume.com"
H = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
body = {"model": "ideogram/ideogram-v4.5", "aspect_ratio": "2:1", "quality": "low",
        "output_format": "jpeg", "prompt": "Wide product banner, plain light background"}
r = requests.post(f"{API}/v1/images", headers=H, json=body, timeout=60)
r.raise_for_status()
if r.status_code == 202:
    raise SystemExit("job still running")
img = Image.open(io.BytesIO(requests.get(r.json()["data"][0]["url"], timeout=60).content)).convert("RGB")
w, h = img.size
new_h = round(w / 1.91)
top = (h - new_h) // 2
out = img.crop((0, top, w, top + new_h))
assert out.width >= 800, f"width {out.width} is under 800"
out.save("x-card.jpg", quality=90)
print(out.size, os.path.getsize("x-card.jpg") <= 3_000_000)

Notes

• The page does not say whether 3 MB means 3,000,000 or 3,145,728 bytes; the script uses the smaller one, 3,000,000 bytes, to be safe.
• Crop trims the top and bottom, so keep text away from those edges.