comfyui-assets

Generating assets with a local ComfyUI

Drive ComfyUI through its HTTP API. You do not need a plugin or MCP server — there are three endpoints.

Talking to it

ComfyUI listens on 127.0.0.1:8188 by default. Start it headless from its venv:

python main.py --listen 127.0.0.1 --port 8188

The API takes a workflow in "API format" — a flat object of node-id → {class_type, inputs}. Export it from the UI with Workflow → Export (API), or hand-author it; it is plain JSON.

// queue
const { prompt_id } = await (await fetch('http://127.0.0.1:8188/prompt', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify({ prompt: workflow, client_id: clientId }),
})).json();

// poll until it appears in history
let out;
while (!out) {
  const hist = await (await fetch(`http://127.0.0.1:8188/history/${prompt_id}`)).json();
  out = hist[prompt_id];
  if (!out) await new Promise((r) => setTimeout(r, 700));
}

// fetch the produced files
for (const node of Object.values(out.outputs)) {
  for (const img of node.images ?? []) {
    const url = `http://127.0.0.1:8188/view?filename=${encodeURIComponent(img.filename)}`
      + `&subfolder=${encodeURIComponent(img.subfolder)}&type=${img.type}`;
    // save the bytes
  }
}

Batch by looping the queue call with a different seed/prompt each time — ComfyUI queues them and works through the list. Keep a modest concurrency (queue depth of a few) rather than firing hundreds at once.

Model choice

For stylised assets (illustration, painterly, game art), prefer SDXL: seconds per image, the deepest LoRA/ControlNet ecosystem. Reserve FLUX for when prompt adherence or legible text really matters — quantised it is roughly an order of magnitude slower per image, which dominates when you are generating and re-rolling a large library.

VRAM guide: SDXL ~8GB, FLUX fp8 ~12GB, FLUX GGUF Q4/Q5 ~6–8GB.

Seamless tiling

Use circular padding in the sampler (ComfyUI: a "seamless"/tiling option or the CircularVAEDecode-style nodes; several tiling custom nodes expose it). Do not fake it by mirroring — mirrored tiles read as obviously symmetrical.