4:1 banner into a 1:4 skyscraper: regenerate instead of cropping

You cannot crop a 4:1 banner into a 1:4 skyscraper without throwing away most of it: the kept strip is 6.25% of the width. Regenerate instead: send the banner as an input_reference and ask Nano Banana 2.1 for aspect_ratio: "1:4", which costs $0.10 at 1K on Sume.

Why cropping fails

A 4:1 banner of height h is 4h wide. A 1:4 slot at the same height is h/4 wide. So you keep (h/4) / (4h) = 1/16 of the width, which is 6.25%, and 93.75% of the picture is gone.

Regenerate from the banner

The reference carries the brand look; the new prompt carries the new layout. Reference URLs must be public HTTPS.

import os, requests

body = {
    "model": "google/nano-banana-2.1",
    "prompt": "Recompose this banner as a tall skyscraper ad: same product, same colors and style, headline space at the top",
    "aspect_ratio": "1:4",
    "resolution": "1K",
    "input_references": [{"type": "image_url", "image_url": {"url": "https://example.com/banner-4x1.jpg"}}],
}
r = requests.post(
    "https://api.sume.com/v1/images",
    headers={"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"},
    json=body, timeout=60,
)
print(r.status_code)  # 200 = image body, 202 = job envelope
if r.status_code == 200:
    out = r.json()
    print(out["data"][0]["url"], out["usage"]["cost"])

Gotchas

• Compare the result with the source: logos and small print can drift when the layout changes.
• A set of four sizes (4:1, 1:4, 1:8, 8:1) is four calls: $0.40 at 1K. Do the first by text, then use it as the reference for the rest.
• The Nano Banana 2.1 ratio list includes 1:4; Pro and sume/auto do not.