# Spectral Noise — Randomly

> 1/f^β synthesised in the frequency domain. One of 63 generators at [Randomly](https://randomly.cluxnei.dev), a library of random generators seeded from verifiable real-world entropy. Free HTTP API, no key, no signup.

## `patterns.spectral` — Spectral Noise

1/f^β synthesised in the frequency domain.

| | |
|---|---|
| **Key** | `patterns.spectral` |
| **Module** | `patterns` |
| **Version** | `1` — a permalink carries this, and a replay against a different version returns `409` rather than something else |
| **Formats** | `application/json`, `text/plain`, `image/png` |
| **Studio** | https://randomly.cluxnei.dev/g/patterns/spectral |
| **API** | `GET https://randomly.cluxnei.dev/api/v1/g/patterns.spectral` |

`value` is a **render spec** — algorithm, parameters, palette and a render key — not pixels. Ask for `format=png` to get the image.

| Parameter | Type | Default | Accepts | What it does |
|---|---|---|---|---|
| `width` | int | `900` | `200` – `2048` | Width |
| `height` | int | `600` | `200` – `2048` | Height |
| `preset` | enum | `brown` | `custom`, `white`, `pink`, `brown`, `black`, `blue`, `violet` | Colour of noise |
| `beta` | float | `1` | `-2.5` – `4` | β — The exponent itself. 0 is white, 1 pink, 2 brown, −1 blue. Only read when the preset is Custom. |
| `contrast` | float | `2.5` | `0.6` – `4` | Contrast — Where the palette's ends are pinned, in standard deviations. A spectral field is Gaussian, so it has tails rather than bounds — stretching to the extremes would leave the whole picture in the middle third of the ramp. |
| `zoom` | float | `1` | `1` – `12` | Zoom — Magnifies the same field. At 1 you see every octave the raster can hold, which for pink noise is mostly grain; wind it up and the low frequencies take over. A 1/f field is scale-free, so this is a real zoom and not a blur. |
| `palette` | enum | `magma` | `golden`, `analogous`, `complementary`, `triadic`, `split`, `viridis`, `magma`, `mono` | Colour |
| `colours` | int | `7` | `2` – `12` | Palette size |
| `contours` | bool | `false` | `true`, `false` | Banding — Quantise into flat bands. On a brown field this draws something very close to a contour map, because that is what a brown field is. |

Out-of-range numbers are **clamped, not rejected**, so a request never fails for being
ambitious — but it may not do what you meant. Unknown keys are dropped and missing ones
fall back to the defaults above.

```bash
curl -s 'https://randomly.cluxnei.dev/api/v1/g/patterns.spectral?width=900&height=600&preset=brown' -H 'Accept: text/plain'
curl -o out.png 'https://randomly.cluxnei.dev/api/v1/g/patterns.spectral?width=900&height=600&preset=brown&format=png'
```

## The receipt

Every result carries one, naming the physical source of the randomness and linking to the
third party's own record of it:

```json
"receipt": {
  "source": "seismic",
  "source_label": "USGS Seismic Feed",
  "class": "C",
  "caveat": "Carries only tens of bits of genuine surprise. Always mixed with the OS CSPRNG.",
  "narrative": "A magnitude 3.6 earthquake, 67 km N of Culebra, Puerto Rico, 39.6 km down — 52 minutes ago.",
  "proof_url": "https://earthquake.usgs.gov/earthquakes/eventpage/us7000th33",
  "mixed_with_csprng": true,
  "degraded": false
}
```

Pick the source with `?source=`, or leave it at the default `auto`:

- **Class A** (Cryptographic) — `csprng`, `anu-qrng`, `random-org`
- **Class B** (Public beacon) — `nist-beacon`, `drand`, `bitcoin`. Published openly — anyone can look this value up after the fact.
- **Class C** (Observational) — `seismic`, `space-weather`, `atmosphere`, `iss`. Carries only tens of bits of genuine surprise. Always mixed with the OS CSPRNG.

## More

- [The full API contract](https://randomly.cluxnei.dev/api.md)
- [Everything in one file](https://randomly.cluxnei.dev/llms-full.txt)
- [The catalogue as JSON](https://randomly.cluxnei.dev/api/v1/generators)
- [This generator in the browser](https://randomly.cluxnei.dev/g/patterns/spectral)