AI tabletop RPG portraits via API: keep one art style on Sume

A party of tabletop RPG portraits looks coherent when every portrait is made against the same style anchor. With the Sume image API that means one text-to-image call for the anchor, then one call per new character with the anchor passed in input_references and a prompt that says "same style as the reference, new subject". Sixteen rows of the catalog accept references; this post uses Flux 2 Pro at $0.0375 per image, so a six-character party costs 7 calls, $0.2625, before any rerolls.

This is the pattern; Sume does not promise identical faces or perfect style lock, and the results depend on your prompts. Check each portrait and re-roll the ones that drift.

Rows that take references

Cheapest reference-capable rows first (all accept at least ten references except Ideogram 4.5 at five).

Anchor, then party

The script makes the anchor, then one portrait per character, each referencing the anchor. Reference URLs must be public HTTPS; the data[].url Sume returns is a hosted URL you can pass straight back. A call that is still running after the 30-second wait returns 202 with a job envelope instead of 200, so check the status code before reading data; see Jobs and results.

import os
import requests

HEADERS = {"Authorization": f"Bearer {os.environ['SUME_API_KEY']}"}
URL = "https://api.sume.com/v1/images"
MODEL = "black-forest-labs/flux.2-pro"

def make(prompt, refs=None):
    body = {"model": MODEL, "prompt": prompt, "aspect_ratio": "1:1"}
    if refs:
        body["input_references"] = [
            {"type": "image_url", "image_url": {"url": u}} for u in refs
        ]
    r = requests.post(URL, headers=HEADERS, json=body, timeout=60)
    r.raise_for_status()
    if r.status_code == 202:
        raise RuntimeError("still running, poll " + r.json()["data"]["status_url"])
    return r.json()["data"][0]["url"]

anchor = make("painted fantasy portrait of a human ranger, bust, parchment-toned background, heavy brush strokes")
print(anchor)
for subject in ["a dwarf cleric", "an elven wizard", "a halfling rogue"]:
    print(subject, make("same style as the reference, new subject: " + subject, [anchor]))

Prompt habits that help

• Put the style in the anchor prompt (medium, palette, framing) and repeat only the subject afterwards.
• Ask for the same framing every time (bust, three-quarter view) so the set tiles in a character sheet.
• Keep names out of the image; add labels in your own layout tool.
• Use n: 4 on a character that matters, then pick one. Four images cost four times the price.

Budget

Ten characters with three rerolls each is 31 calls, about $1.16 on Flux 2 Pro. On Qwen Image at $0.025 it is $0.775. A failed call is not billed, so retrying after an error does not add to the total.