Chart.js

Chart.js ist eine Library zum Erstellen von Diagrammen. Die Diagramme werden über WegGl gerendert.

Man kann sehr effektiv Diagramme erstellen und die Ausgabe recht umfangreich anpassen.

Chart.js - Snippets

Chart.js - Snippets

Chart.js - SVG Export

Plugin: http://gliffy.github.io/canvas2svg/

Beispielskript:

/*
PNG AND SVG EXPORT (for Illustrator)
Jeff Thompson | 2021 | jeffreythompson.org

Online charts are great, but what if you want to share
them on social media, use them in print projects, etc?
With a little tweaking, we can export and download
any chart we make as a PNG and SVG!

SVGs are vector graphics, meaning we can also open
them in Illustrator and access all the shapes! This is
great if you want to create a base chart in code, then
style it in Illustrator to make it super cool.

Note! Your SVG may look cut off when viewing in
the web browser. Fear not: if you open it in Illustrator
you'll see everything there :)

DATA SOURCE
+ https://en.wikipedia.org/wiki/World_population

MORE INFO
+ Uses canvas2svg.js
  http://gliffy.github.io/canvas2svg

CHALLENGES
1. Try opening the SVG in Illustrator: can you ungroup
   everything and change colors and text?

*/

// set the output dimensions (helpful
// especially for PNG)
let width =  900;
let height = 600;

// (scroll down for more details...)
let data = [ 585,  660,  710,  978,  1650, 6127, 8549, 10152, 10875 ];
let labels = [ 1500, 1600, 1700, 1800, 1900, 2000, 2030, 2060, 2100 ];
let title = 'World Population (in millions)';

let options = {
  type: 'bar',
  data: {
    labels: labels,
    datasets: [{
      backgroundColor: 'rgb(255,150,0)',
      barPercentage:   1.0,
      data:            data,
      label:           'Population (in millions)'
    }]
  },
  options: {  
    title: {
      display: true,
      text: title
    },
    legend: {
      display: false
    },
    
    // these need to be set to false
    // for export!
    animation:  false,
    responsive: false
  }
}

// set the chart's size based on the
// values we set at the top
let context =    document.getElementById('canvas');
context.width =  width;
context.height = height;

// create the chart
let chart = new Chart(document.getElementById('canvas'), options);

// and generate the PNG and SVG links!
// (the code that does this is in the 'libs'
// folder > export.js)

// arguments: filename, link text, chart we created
createPngLink('chart.png', 'Export PNG, ', chart);

// arguments: filename, link text, the chart, and its settings
createSvgLink('chart.svg', 'SVG', chart, options);

export.js

function createPngLink(filename, linkText, chart) {
  if (chart.options.animation !== false) {
    console.warn('Cannot create PNG: "animation" is not set to false (see the options section)');
    return;
  }
  if (chart.options.responsive !== false) {
    console.warn('Cannot create PNG: "responsive" is not set to false (see the options section)');
    return;
  }

  // create the download link
  let link = document.createElement('a');
  link.href = chart.toBase64Image();
  link.download = filename;
  link.text = linkText;
  
  // and add it to the page
  document.getElementById('wrapper').appendChild(link);
}


function createSvgLink(filename, linkText, chart, chartSettings) {
  if (chart.options.animation !== false) {
    console.warn('Cannot create SVG: "animation" is not set to false (see the options section)');
    return;
  }
  if (chart.options.responsive !== false) {
    console.warn('Cannot create SVG: "responsive" is not set to false (see the options section)');
    return;
  }

  tweakLib();

  // get the dimensions of our original chart
  let chartCanvas = document.getElementById('canvas');
  let width =  chartCanvas.offsetWidth;
  let height = chartCanvas.offsetHeight;

  // create an svg version of the chart
  let svgContext = C2S(width, height);
  let svgChart = new Chart(svgContext, chartSettings);

  // create download link
  let link = document.createElement('a');
  link.href = 'data:image/svg+xml;utf8,' + encodeURIComponent(svgContext.getSerializedSvg());
  link.download = filename;
  link.text = linkText;

  // add link to the page
  document.getElementById('wrapper').appendChild(link);
}


// some tweaks to the canvas2svg library are required for this to work
// via: https://stackoverflow.com/questions/62249315/export-canvas-to-svg-file
function tweakLib() {
  C2S.prototype.getContext = function(contextId) {
    if (contextId === '2d' || contextId === '2D') {
      return this;
    }
    return null;
  }
  C2S.prototype.style = function() {
    return this.__canvas.style;
  }
  C2S.prototype.getAttribute = function(name) {
    return this[name];
  }
  C2S.prototype.addEventListener = function(type, listener, eventListenerOptions) {
    // nothing to do here, but we need this function :)
  }
}