A Ruby client for the quickchart.io chart image API.

Use the lib/quickchart.rb library in this project, or install as a Ruby gem:

gem install quickchart

This library provides a QuickChart class. Import and instantiate it. Then set properties on it and specify a Chart.js config:

require 'quickchart'

qc = QuickChart.new(
  {
    type: "bar",
    data: {
      labels: ["Hello world", "Test"],
      datasets: [{
        label: "Foo",
        data: [1, 2]
      }]
    }
  },
  width: 600,
  height: 300,
  device_pixel_ratio: 2.0,
)

Use get_url() on your quickchart object to get the encoded URL that renders your chart:

puts qc.get_url
# https://quickchart.io/chart?c=%7B%22type%22%3A%22bar%22%2C%22data%22%3A%7B%22labels%22%3A%5B%22Hello+world%22%2C%22Test%22%5D%2C%22datasets%22%3A%5B%7B%22label%22%3A%22Foo%22%2C%22data%22%3A%5B1%2C2%5D%7D%5D%7D%7D&w=600&h=300&bkg=%23ffffff&devicePixelRatio=2.0&f=png

If you have a long or complicated chart, use get_short_url() to get a fixed-length URL using the quickchart.io web service (note that these URLs only persist for a short time unless you have a subscription):

puts qc.get_short_url
# https://quickchart.io/chart/render/f-a1d3e804-dfea-442c-88b0-9801b9808401

The URLs will render an image of a chart:

The QuickChart class constructor accepts the following parameters. config is the only required parameter, the rest are optional:

The actual Chart.js chart configuration.

Width of the chart image in pixels. Defaults to 500

Height of the chart image in pixels. Defaults to 300

Format of the chart. Defaults to png. svg is also valid.

The background color of the chart. Any valid HTML color works. Defaults to #ffffff (white). Also takes rgb, rgba, and hsl values.

The device pixel ratio of the chart. This will multiply the number of pixels by the value. This is usually used for retina displays. Defaults to 1.0.

QuickChart API key (not required)

Sets the Chart.js version to use (e.g. 2.9.4 or 3.8.0). Valid options are described in the documentation.

There are two ways to get a URL for your chart object.

Returns a URL that will display the chart image when loaded.

Uses the quickchart.io web service to create a fixed-length chart URL that displays the chart image. Returns a URL such as https://quickchart.io/chart/render/f-a1d3e804-dfea-442c-88b0-9801b9808401.

Note that short URLs expire after a few days for users of the free service. You can subscribe to keep them around longer.

Returns a binary string representing the chart image

Write the image to a file

For example:

qc.to_file("/tmp/myfile.png")

Checkout the examples directory to see other usage.