jdtzmn / ChartjsNodeCanvas

A node renderer for Chart.js using canvas.

chartjs-node-canvas

A node renderer for Chart.js using canvas.

Provides and alternative to chartjs-node that does not require jsdom (or the global variables that this requires) and allows chartJS as a peer dependency, so you can manage its version yourself.

Installation

npm i chartjs-node-canvas

Features

• Supports all Chart JS features and charts.
• Uses canvas-prebuilt, so hopefully no nasty issues with node-gyp.
• No heavy DOM virtualization libraries, thanks to a pull request to chart.js allowing it to run natively on node, requiring only a Canvas API.
• Chart JS is a peer dependency, so you can bump and manage it yourself.
• Provides a callback with the global ChartJS variable, so you can use the Global Configuration.
• Uses fresh-require for each instance of CanvasRenderService, so you can mutate the ChartJS global variable seperatly within each instance.

Usage

const { CanvasRenderService } = require('chartjs-node-canvas');

(async () => {
    const width = 400; //px
    const height = 400; //px
    const configuration = {
        ... // See https://www.chartjs.org/docs/latest/configuration
    };
    const canvasRenderService = new CanvasRenderService(width, height, (ChartJS) => {
        // See https://www.chartjs.org/docs/latest/configuration/#global-configuration
        ChartJS.defaults.global.responsive = true;
    });
    const image = await canvasRenderService.renderToBuffer(configuration);
    const dataUrl = await canvasRenderService.renderToDataURL(configuration); // image/png
    const stream = canvasRenderService.renderToStream(configuration);
})();

Full Example

const { CanvasRenderService } = require('chartjs-node-canvas');

const width = 400;
const height = 400;
const configuration = {
    type: 'bar',
    data: {
        labels: ['Red', 'Blue', 'Yellow', 'Green', 'Purple', 'Orange'],
        datasets: [{
            label: '# of Votes',
            data: [12, 19, 3, 5, 2, 3],
            backgroundColor: [
                'rgba(255, 99, 132, 0.2)',
                'rgba(54, 162, 235, 0.2)',
                'rgba(255, 206, 86, 0.2)',
                'rgba(75, 192, 192, 0.2)',
                'rgba(153, 102, 255, 0.2)',
                'rgba(255, 159, 64, 0.2)'
            ],
            borderColor: [
                'rgba(255,99,132,1)',
                'rgba(54, 162, 235, 1)',
                'rgba(255, 206, 86, 1)',
                'rgba(75, 192, 192, 1)',
                'rgba(153, 102, 255, 1)',
                'rgba(255, 159, 64, 1)'
            ],
            borderWidth: 1
        }]
    },
    options: {
        scales: {
            yAxes: [{
                ticks: {
                    beginAtZero: true,
                    callback: (value: number) => '$' + value
                } as any
            }]
        }
    }
};
const chartCallback = (ChartJS) => {

    ChartJS.defaults.global.responsive = true;
    ChartJS.defaults.global.maintainAspectRatio = false;
};

(async () => {
    const canvasRenderService = new CanvasRenderService(width, height, chartCallback);
    const image = await canvasRenderService.renderToBuffer(configuration);
    const dataUrl = await canvasRenderService.renderToDataURL(configuration);
    const stream = canvasRenderService.renderToStream(configuration);
})();