Upscale an image

image.upscale increases an image’s resolution on a hosted one-step diffusion model. Ask for a factor or a target height and the other side follows the source aspect ratio. The result is a png returned as a signed URL, the same async job shape as everything else on Rendobar. This model reconstructs detail rather than only sharpening what is already there. A compressed or soft source comes back rebuilt, not just enlarged. That is a different job from a faithful resize, and it is worth knowing which one you asked for. This is one product in Rendobar’s Generation API.

import { createClient, outputUrl } from "@rendobar/sdk";

const client = createClient({ apiKey: "rb_YOUR_KEY" });

// jobs.run submits and waits for the finished job in one call.
const job = await client.jobs.run({
  type: "image.upscale",
  inputs: { source: "https://example.com/photo.jpg" },
  params: {
    sizing: { mode: "factor", factor: 2 },
  },
});

console.log(outputUrl(job)); // signed URL to the png

curl -X POST "https://api.rendobar.com/jobs" \
  -H "Authorization: Bearer rb_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "image.upscale",
    "inputs": { "source": "https://example.com/photo.jpg" },
    "params": {
      "sizing": { "mode": "factor", "factor": 2 }
    }
  }'
# Returns { "data": { "id": "job_...", "status": "waiting" } }.
# Poll GET /jobs/{id} until "status": "complete".

import requests, time

base = "https://api.rendobar.com"
headers = {"Authorization": "Bearer rb_YOUR_KEY"}

job = requests.post(
    f"{base}/jobs",
    headers=headers,
    json={
        "type": "image.upscale",
        "inputs": {"source": "https://example.com/photo.jpg"},
        "params": {"sizing": {"mode": "factor", "factor": 2}},
    },
).json()["data"]

while job["status"] not in ("complete", "failed", "cancelled"):
    time.sleep(1)
    job = requests.get(f"{base}/jobs/{job['id']}", headers=headers).json()["data"]

print(job["output"]["file"]["url"])  # the png

Sizing

sizing is a union, because “twice as big” and “2160 pixels tall” are different questions and only one can be answered per request.

{ "sizing": { "mode": "factor", "factor": 2 } }

{ "sizing": { "mode": "height", "height": 2160 } }

Either way the output lands on exactly the size you asked for, as long as it fits on the GPU. The default is factor: 2. See Size limits for what happens when it does not.

Parameters

Parameter	Default	Description
`model`	`seedvr2-3b`	`seedvr2-3b` or `seedvr2-7b`. The 7B is the larger checkpoint, offered as an option rather than an upgrade.
`sizing`	`{ mode: "factor", factor: 2 }`	How large the output should be.
`inputNoise`	`0.1`	Artifact reduction, 0 to 1. Higher is smoother and reconstructs less. 0.1 to 0.3 is the useful band.
`inputScale`	`1`	Shrink the source before upscaling, 0.25 to 1. Below 1 gives the model less to preserve and more to rebuild.
`passes`	auto	Run the model repeatedly, each pass covering an equal share of the total factor. Left unset it follows the factor, keeping every step near a doubling. Costs one full render per pass.
`latentNoise`	`0`	Softens excessive detail, 0 to 1. Reach for it when a result looks overcooked rather than soft. 0.05 to 0.15 is the useful band.
`colorCorrection`	`lab`	How colour is matched back to the source: `lab`, `wavelet`, `wavelet_adaptive`, `hsv`, `adain`, `none`. `lab` is the most faithful.
`seed`	`42`	The same seed returns the same image. This model reconstructs detail rather than copying it, so a different seed is a different plausible result.

Every parameter is optional. Send none of them and you get the defaults above, which are the settings this job was tuned on.

Choosing a factor

2x is where this model does its best work. It reconstructs about one doubling, so a larger factor adds pixels faster than it adds detail. Ask for 4x and the job runs two 2x steps automatically, which looks close to a native 2x and costs two renders. A single large step is available with passes: 1, and looks worse.

Choosing inputScale

Leave it at 1 for photographs. Lowering it hands the model less to work from and more to invent, which suits a clean uncompressed source and hurts a compressed one, where the reconstruction follows the compression artifacts instead of the subject.

Transparency

A transparent png stays transparent. Alpha is upscaled alongside the colour channels rather than flattened, so a logo keeps its edge.

The output

A completed job carries a single png file in output.file. output.data is null, because upscaling writes a file rather than computing an answer. png rather than webp on purpose. Re-compressing lossily is the one thing that would undo the point of an upscale.

{
  "data": null,
  "file": {
    "url": "https://api.rendobar.com/dl/job_abc123?token=<token>",
    "path": "output.png",
    "type": "image",
    "size": 4194304,
    "meta": { "format": "png", "width": 3840, "height": 2160 }
  },
  "expiresAt": 1735689600000
}

Size limits

There is no product cap on how large an output you can ask for. The bound is what the GPU can physically hold. Ask for more than that and the job still runs. The output is capped to the largest size that fits, keeping your source’s aspect ratio, and the job log says what happened:

requested 2730x4096 (11.2 MP) is larger than the 9.9 MP this GPU can hold,
so it was capped to 2568x3852 (about 1.87x this 1365x2048 source)

Read the real dimensions off output.file.meta rather than assuming they match what you asked for. Everything under the ceiling is untouched and lands exactly on the requested size. The limit is on output pixels, not on the factor, so how far you can go depends on the source. A 1365x2048 photo is already 2.8 megapixels, and 2x of it is 11.2, which is why the example above caps at under 2x. A small source can go to 4x and beyond. The ceiling also depends on the model. seedvr2-7b holds about twice the weights of seedvr2-3b and keeps less room for the image, so it caps roughly 40% sooner. If you are working near the limit, seedvr2-3b is the one that goes further, and it is also the default.

Getting Started

Concepts

Jobs

Integrations

Support

Upscale an image

Upscale an image

Sizing

Parameters

Choosing a factor

Choosing inputScale

Transparency

The output

Size limits

​Upscale an image

​Sizing

​Parameters

​Choosing a factor

​Choosing inputScale

​Transparency

​The output

​Size limits

​Related

Upscale an image

Sizing

Parameters

Choosing a factor

Choosing inputScale

Transparency

The output

Size limits

Related