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quickchart-ruby

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

Installation

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

gem install quickchart

Usage

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:

Creating the chart object

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

config: hash or string (required)

The actual Chart.js chart configuration.

width: int

Width of the chart image in pixels. Defaults to 500

height: int

Height of the chart image in pixels. Defaults to 300

format: string

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

background_color: string

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

device_pixel_ratio: float

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.

key: string

QuickChart API key (not required)

version: string

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

Getting URLs

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

get_url: string

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

get_short_url: string

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.

Other outputs

to_blob: binary string

Returns a binary string representing the chart image

to_file(path: string)

Write the image to a file

For example:

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

More examples

Checkout the examples directory to see other usage.