JSON to chart

JSON to chart is an API that turns data into a chart image (bar, line, pie, doughnut or radar). Send your numbers as JSON and get back a ready-to-use image for an email, a report or a Slack message, with nothing to design by hand.

How it works

You send the chart type, the labels (X-axis categories, or the name of each slice) and one or more series of numbers, and get back the generated image: PNG by default, base64-encoded inside a JSON response.

Since the input is always a data structure, this tool only accepts a JSON body (there's no "paste the raw file" mode).

All you need

Your API key. Create it in your dashboard with "+ Create key". It's shown only once, so copy and save it.
In your automation platform, an "HTTP Request" step (n8n, Make, Zapier, Pipedream… all have one).
Your data as numbers: the tool does the rest.

How to use it in n8n (step by step)

In the HTTP Request node:

Method: POST
URL: https://api.cofferdock.com/chart
Send Headers: on → add two: x-api-key = your key, and Content-Type = application/json
Send Body: on → Body Content Type: JSON → { "type": "bar", "labels": ["Jan", "Feb", "Mar"], "series": [{ "name": "Sales", "data": [10, 20, 15] }] }

By default the response is already a JSON with the image as base64 inside the image field, so there's nothing else to change under Options → Response. If you'd rather get the image directly (to attach it as binary data), add "output": "binary" to the body and choose Response Format: File under Options → Response, same as other Cofferdock tools.

In Make (HTTP → Make a request module): same method and URL, Body type: Raw, Content type: JSON, with the same body.

Options (inside the JSON)

Option	Default	What it does
`type`	-	Required. Chart type: `bar`, `line`, `pie`, `doughnut` or `radar`.
`labels`	-	Required. 1 to 50 strings: X-axis categories (bar/line) or the name of each slice/indicator (pie/radar).
`series`	-	Required. 1 to 10 series, each `{ "name": "...", "data": [...] }` with as many numbers as `labels`. `pie`/`doughnut` only support 1 series.
`title`	-	Chart title (optional).
`width` / `height`	800 / 500	Size in pixels (between 200 and 2000).
`format`	`png`	`png` or `svg`.
`output`	`json`	`json` (base64 image inside a JSON) or `binary` (the image directly).

API overview

Endpoint: POST https://api.cofferdock.com/chart
Auth: header x-api-key: YOUR_KEY.
Input: application/json ONLY.
Output: JSON with the base64 image by default; with "output": "binary" it returns the image directly (image/png or image/svg+xml depending on format).
Engine: Apache ECharts in server mode (no browser, no canvas), rasterized to PNG with sharp when needed.
Limits: 30 requests/min per IP. 1 chart = 1 credit, regardless of type or size.

Options

Option	Default	Description
`type`	-	Required. `bar \| line \| pie \| doughnut \| radar` (400 if not in the list).
`labels`	-	Required. Array of 1 to 50 non-empty strings, up to 100 characters each.
`series`	-	Required. Array of 1 to 10 `{ name?, data }` objects. `data` must match `labels`' length and contain only finite numbers. `name` is optional (up to 100 characters; defaults to `"Series N"`). `pie`/`doughnut`: 400 if `series.length > 1`.
`title`	-	Optional string, up to 200 characters.
`width` / `height`	800 / 500	Number, clamped to [200, 2000].
`format`	`png`	`png` or `svg`.
`output`	`json`	`json` or `binary`.

Examples

curl (bar chart straight to PNG):

curl -X POST "https://api.cofferdock.com/chart" \
  -H "x-api-key: YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"type":"bar","labels":["Jan","Feb","Mar"],"series":[{"name":"Sales","data":[10,20,15]}],"output":"binary"}' \
  -o chart.png

JavaScript (Node 18+):

const r = await fetch('https://api.cofferdock.com/chart', {
  method: 'POST',
  headers: { 'x-api-key': 'YOUR_KEY', 'Content-Type': 'application/json' },
  body: JSON.stringify({
    type: 'pie',
    title: 'Breakdown',
    labels: ['A', 'B', 'C'],
    series: [{ data: [40, 25, 35] }],
  }),
});
const { image } = await r.json();
require('fs').writeFileSync('chart.png', Buffer.from(image, 'base64'));

Python:

import base64, requests
r = requests.post(
    'https://api.cofferdock.com/chart',
    headers={'x-api-key': 'YOUR_KEY', 'Content-Type': 'application/json'},
    json={'type': 'line', 'labels': ['Jan', 'Feb', 'Mar'], 'series': [{'data': [10, 20, 15]}], 'output': 'binary'},
)
open('chart.png', 'wb').write(r.content)

Response with `output=json` (default)

{ "success": true, "image": "iVBORw0KGgoAAAANSUhEUgAA…", "mime_type": "image/png",
    "meta": { "format": "png", "width": 800, "height": 500, "used": 12, "remaining": 488 } }

What you get back

By default, a JSON with the image as base64: handy for using it right away in the next step of your flow (for example, embedding it in an email as data:image/png;base64,…) with no extra steps. With "output": "binary" you get the image directly, useful when the next step expects a binary file.