Open Graph image 1200x630 with an AI API: generate 16:9, then crop

Generate at aspect_ratio: "16:9", then center-crop to 1200 x 630 in code. Meta's sharing guide says to 'use images that are at least 1200 x 630 pixels' and to 'keep your images as close to 1.91:1 aspect ratio as possible' so they show in Feed without cropping, with a file no larger than 8 MB (Meta for Developers, read 2026-10-01). Sume's normalized ratio list has 16:9 (1.78) and 2:1 (2.0) but no 1.91:1, so the final trim is a local step.

16:9 is 1.78 and 1200 x 630 is 1.905, so you lose a thin band at the top and bottom. Tell the prompt to keep the subject and any headline in the middle 80 percent of the frame.

What are the numbers?

Read from each source on the dates shown.

How do I crop?

Download the result, resize to width 1200, then crop the height to 630 around the center.

import io
import os
import requests
from PIL import Image

H = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
r = requests.post("https://api.sume.com/v1/images", headers=H, timeout=60,
    json={"model": "openai/gpt-image-2.5", "aspect_ratio": "16:9",
          "prompt": "clean blog header, laptop on a desk, empty centre space"})
r.raise_for_status()
raw = requests.get(r.json()["data"][0]["url"], timeout=60).content
img = Image.open(io.BytesIO(raw)).convert("RGB")
img = img.resize((1200, round(img.height * 1200 / img.width)))
top = (img.height - 630) // 2
img.crop((0, top, 1200, top + 630)).save("og.jpg", quality=90)
print("og.jpg", os.path.getsize("og.jpg"), "bytes")

Prompt for a safe crop zone

Because the crop removes about 6 percent of the height, ask for 'subject centered, generous empty margin at top and bottom'. If you add text later, draw it yourself with Pillow on the cropped image, so spelling and position are exact.

Test the result in a link preview tool or by sharing the URL to yourself before announcing a page. Platforms cache preview images, so a wrong first image can stick for a while.

Limits

If the 16:9 result is under 1200 pixels wide, the resize upscales it; pick a higher resolution where the model lists one. Do not ask the model to draw the site name in small type, because crops cut it and text can be misspelled. JPEG at quality 90 keeps most files well under 8 MB, but check the printed byte count.