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API · /gradient-api

Gradient API

healthy 4,550 Subscribers

Generate colour gradients and colour scales programmatically. Produce an evenly-spaced scale of N colours between two or more stops (interpolated in a perceptually smooth colour space — lab, lch, oklab, oklch — or plain rgb/hsl), get a single interpolated colour at any position between two colours, and build a ready-to-paste CSS gradient string (linear with any angle, or radial) from a list of stops. Colours accept hex (#f00, #ff0000) or CSS names (red, steelblue). Perfect for data-visualisation colour ramps, heatmaps, chart palettes, theme generation and UI backgrounds. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. Distinct from colour conversion / harmonious palettes (one base colour) and image palette extraction.

#gradient #color #css #data-visualization #design #developer-tools
api.oanor.com/gradient-api
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Machine-readable spec so AI agents can integrate this API.

/api/gradient-api/openapi.json
/api/gradient-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
89 ms
Server probes · 24h
Subscribers
4,550
active
Total calls
56
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 1,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,000 calls/month
  • 2 req/sec
  • Scale + interpolate + CSS
  • No credit card
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Starter

€2.30 /month

  • 8,500 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 8.5k calls/month
  • 8 req/sec
  • Perceptual colour spaces (lab/oklch)
  • Email support
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Pro

€21.40 /month

  • 137,000 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 137k calls/month
  • 20 req/sec
  • Data-viz / theme pipelines
  • Priority support
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Mega

€57.40 /month

  • 705,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 705k calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Slope & Grade API

Slope and grade maths as an API, computed locally and deterministically. The convert endpoint converts a slope between every common form — percent grade, angle in degrees, a ratio such as 1:12, per mille and rise-per-run — where the slope m = rise ÷ run = tan(angle). The distance endpoint relates the run (horizontal), the rise (vertical) and the slope distance (the hypotenuse) of a right-triangle slope: give any two, optionally with the grade or angle, and it returns the rest. The ramp endpoint sizes a wheelchair or ADA ramp — from a rise and a maximum slope (defaulting to 1:12, the ADA maximum of 8.33%) it returns the required run and total ramp length, and if you supply an actual run it checks whether the ramp is within the limit. Everything is computed locally and deterministically, so it is instant and private. Ideal for civil-engineering and surveying tools, road, trail and accessibility apps, construction and ramp design, and mapping software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is slope and grade geometry; for roof pitch specifically use a roofing API.

api.oanor.com/slope-api

Color Distance API

CIE colour science as an API: convert colours through the device-independent spaces and measure how different two colours really look. The convert endpoint takes a colour as hex, RGB or CIELAB and returns it in sRGB hex, RGB, CIE XYZ and CIELAB (D65 white point). The distance endpoint computes the perceptual difference between two colours with all three standard Delta-E formulas — CIE76 (plain Lab distance), CIE94, and CIEDE2000, the modern and most accurate metric — and tells you whether the difference is perceptible. The nearest endpoint finds the closest named colour to any colour by CIEDE2000. This is the maths behind colour matching, print and brand-colour QC, and tolerancing — distinct from simple hex/RGB/HSL conversion. Everything is computed locally and deterministically, so it is instant and private. Ideal for print and prepress, brand-colour compliance, textile and paint matching, image processing and computer vision, and design tooling. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is CIE colour difference; for hex/RGB/HSL/CMYK conversion, palettes and WCAG contrast use a colour API.

api.oanor.com/colordelta-api

Color Temperature API

Turn physical light into RGB colours — entirely locally. The kelvin endpoint converts a colour temperature in Kelvin into the RGB colour of a black body at that temperature: warm candle and incandescent tones below 3000 K, neutral and daylight whites around 5000–6500 K, and cool bluish light above, using Tanner Helland's widely-used approximation and returning hex, an rgb() string and a plain-English description (candlelight, warm white, neutral, daylight, cool). The wavelength endpoint converts a wavelength of visible light in nanometres (380–780 nm) into the approximate RGB colour the human eye perceives, with the natural intensity fall-off at the violet and red edges of the spectrum, and names the band (violet, blue, cyan, green, yellow, orange, red). Everything is computed locally and deterministically, so it is instant and private. Ideal for lighting and smart-bulb apps, photography and white-balance tools, data-visualisation of temperature or spectra, theming and UI accents, and science and education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. These are perceptual approximations, not colorimetric CIE conversions; for hex/RGB/HSL conversion and palettes use a colour API.

api.oanor.com/colortemp-api

Color Name API

Name any colour. The nearest endpoint takes a colour as a hex, an rgb() value, an r,g,b triple or another name and returns the closest of the 140+ CSS named colours — matched perceptually with CIE76 Lab distance, not naive RGB, so the name actually looks right — along with the distance and whether it is an exact match. The name endpoint resolves a CSS colour keyword (e.g. rebeccapurple, cornflowerblue) to its hex and RGB, and list returns the whole named-colour set. Perfect for design tools and pickers, accessibility and theming, turning brand hex codes into human labels, and naming colours in generated palettes. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. Distinct from colour conversion / palette / contrast tooling, which does not name colours.

api.oanor.com/colorname-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Gradient API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Gradient API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Gradient API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Gradient API cost?
Gradient API has a free tier with 100 calls / month. Paid plans start at €2.30 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Gradient API GDPR-compliant?
All requests to Gradient API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/gradient-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/gradient-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/gradient-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/gradient-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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