9:16 story image from Sume, then resize to 1080x1920 with Pillow

To get a 1080x1920 vertical file from POST /v1/images, request aspect_ratio: "9:16" and resize the result with Pillow. The docs say explicit pixels are not served in v1 (read 2026-10-03), and size is only a shorthand for a resolution tier. Every one of the 19 catalog models lists 9:16, so the choice is about price: Qwen Image and Grok Imagine are $0.025 per image.

What the API takes

On /v1/images you control shape with aspect_ratio and, on some models, a resolution tier (0.5K, 1K, 2K, 4K on the Nano Banana rows; 1K and 2K on Ideogram 4.5 and Imagen 4 Ultra). The exact pixel count comes back with the file, so measure it instead of assuming.

Cover-crop, don't stretch

Scale the image so it covers 1080x1920, then trim the overflow equally from both sides. A stretch would distort faces and logos. A model that returns a ratio slightly off 9:16 will lose only a few pixels.

import os, requests
from io import BytesIO
from PIL import Image, ImageOps

r = requests.post("https://api.sume.com/v1/images", timeout=120,
    headers={"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"},
    json={"model": "qwen/qwen-image", "aspect_ratio": "9:16",
          "prompt": "poster-style illustration of a lighthouse at dusk, empty sky in the top third"})
if r.status_code != 200:
    raise SystemExit(f"{r.status_code}: {r.text[:200]}")
raw = requests.get(r.json()["data"][0]["url"], timeout=60).content
im = Image.open(BytesIO(raw)).convert("RGB")
print("returned", im.size)
ImageOps.fit(im, (1080, 1920), Image.LANCZOS).save("story.jpg", quality=90)

Keep the safe areas yourself

Story apps overlay their own buttons and captions at the top and bottom. Ask for an empty top and bottom third in the prompt, and place text in your own editor.

Upscaling

If a model returns fewer pixels than 1080 wide, the resize enlarges the picture and softens it. Use a higher tier where one exists, such as 2K on Nano Banana 2, which costs $0.15, or render once and enlarge with an upscaler.