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Export SVG D3 visualization to PNG or JPEG
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.block
license: mit
Raw
README.md

This example shows how to properly export a D3 SVG visualization to an image (png/jpeg) taking into account external css styles and embedded images. The code uses small FileSaver.js library to save generated images and Canvas-to-Blob.js library to ensure browser compatibility.

Raw
index.html
<!DOCTYPE html>
<html lang="en">
<head>
<title>How to properly export SVG D3 visualization to PNG or JPEG</title>
<meta charset="utf-8">
<script src="https://cdn.rawgit.com/eligrey/canvas-toBlob.js/f1a01896135ab378aa5c0118eadd81da55e698d8/canvas-toBlob.js"></script>
<script src="https://cdn.rawgit.com/eligrey/FileSaver.js/e9d941381475b5df8b7d7691013401e171014e89/FileSaver.min.js"></script>
<script src="https://d3js.org/d3.v3.min.js"></script>
<style type="text/css">
.blendCircle {
mix-blend-mode: multiply;
}
</style>
</head>
<body>
<div>
<button id='saveButton'>Export my D3 visualization to PNG</button>
</div>
</body>
<script type="text/javascript">
// Let's create a mock visualization
var width = 300, height = 300;
var circleSizeMax = 15;
var rMax = Math.min(width,height)/2 - circleSizeMax;
var radius = d3.scale.linear().range([0,rMax]);
var angle = d3.scale.linear().range([0,2*Math.PI]);
var size = d3.scale.linear().range([0,circleSizeMax]);
var color = d3.scale.ordinal().range(['#fcfb3c','#fcf900','#ff825a','#ffd2cb','#71d362','#ffd16f','#ff3d5d','#ff7218','#04b3f3','#bce5ac','#6e0215','#69D2E7','#A7DBDB','#E0E4CC','#F38630','#E94C6F','#542733','#5A6A62','#C6D5CD','#DB3340','#E8B71A','#F7EAC8','#1FDA9A','#588C73','#F2E394','#F2AE72','#D96459','#D0C91F','#85C4B9','#008BBA','#DF514C','#00C8F8','#59C4C5','#FFC33C','#FBE2B4','#5E412F','#FCEBB6','#78C0A8','#F07818','#DE4D4E','#DA4624','#DE593A','#FFD041','#B1EB00','#53BBF4','#FF85CB','#FF432E','#354458','#3A9AD9','#29ABA4','#E9E0D6','#4298B5','#ADC4CC','#92B06A','#E19D29','#BCCF02','#5BB12F','#73C5E1','#9B539C','#FFA200','#00A03E','#24A8AC','#0087CB','#260126','#59323C','#F2EEB3','#BFAF80','#BFF073','#0DC9F7','#7F7F7F','#F05B47','#3B3A35','#20457C','#5E3448','#FB6648','#E45F56','#A3D39C','#7ACCC8','#4AAAA5','#DC2742','#AFA577','#ABA918','#8BAD39','#F2671F','#C91B26','#9C0F5F','#60047A','#0F5959','#17A697','#638CA6','#8FD4D9','#83AA30','#1499D3','#4D6684','#3D3D3D','#333333','#424242','#00CCD6','#EFEFEF','#CCC51C','#FFE600','#F05A28','#B9006E','#F17D80','#737495','#68A8AD','#C4D4AF']);
var x = function(d) { return radius( d.r ) * Math.cos( angle( d.angle ) ); };
var y = function(d) { return radius( d.r ) * Math.sin( angle( d.angle ) ); };
var svg = d3.select('body').append('svg')
.attr('width', width)
.attr('height',height);
var chart = svg.append('g').attr('transform','translate('+[width/2,height/2]+')');
var data = d3.range(150).map( function(d) { return {r: Math.random(), angle: Math.random(), size: Math.random() }; });
chart.selectAll('cirle')
.data(data).enter()
.append('circle')
.attr('class','blendCircle')
.attr({
cx: x,
cy: y,
r: function(d) { return size(d.size); },
fill: function(d,i) { return color(i); }
});
// Set-up the export button
d3.select('#saveButton').on('click', function(){
var svgString = getSVGString(svg.node());
svgString2Image( svgString, 2*width, 2*height, 'png', save ); // passes Blob and filesize String to the callback
function save( dataBlob, filesize ){
saveAs( dataBlob, 'D3 vis exported to PNG.png' ); // FileSaver.js function
}
});
// Below are the functions that handle actual exporting:
// getSVGString ( svgNode ) and svgString2Image( svgString, width, height, format, callback )
function getSVGString( svgNode ) {
svgNode.setAttribute('xlink', 'http://www.w3.org/1999/xlink');
var cssStyleText = getCSSStyles( svgNode );
appendCSS( cssStyleText, svgNode );
var serializer = new XMLSerializer();
var svgString = serializer.serializeToString(svgNode);
svgString = svgString.replace(/(\w+)?:?xlink=/g, 'xmlns:xlink='); // Fix root xlink without namespace
svgString = svgString.replace(/NS\d+:href/g, 'xlink:href'); // Safari NS namespace fix
return svgString;
function getCSSStyles( parentElement ) {
var selectorTextArr = [];
// Add Parent element Id and Classes to the list
selectorTextArr.push( '#'+parentElement.id );
for (var c = 0; c < parentElement.classList.length; c++)
if ( !contains('.'+parentElement.classList[c], selectorTextArr) )
selectorTextArr.push( '.'+parentElement.classList[c] );
// Add Children element Ids and Classes to the list
var nodes = parentElement.getElementsByTagName("*");
for (var i = 0; i < nodes.length; i++) {
var id = nodes[i].id;
if ( !contains('#'+id, selectorTextArr) )
selectorTextArr.push( '#'+id );
var classes = nodes[i].classList;
for (var c = 0; c < classes.length; c++)
if ( !contains('.'+classes[c], selectorTextArr) )
selectorTextArr.push( '.'+classes[c] );
}
// Extract CSS Rules
var extractedCSSText = "";
for (var i = 0; i < document.styleSheets.length; i++) {
var s = document.styleSheets[i];
try {
if(!s.cssRules) continue;
} catch( e ) {
if(e.name !== 'SecurityError') throw e; // for Firefox
continue;
}
var cssRules = s.cssRules;
for (var r = 0; r < cssRules.length; r++) {
if ( contains( cssRules[r].selectorText, selectorTextArr ) )
extractedCSSText += cssRules[r].cssText;
}
}
return extractedCSSText;
function contains(str,arr) {
return arr.indexOf( str ) === -1 ? false : true;
}
}
function appendCSS( cssText, element ) {
var styleElement = document.createElement("style");
styleElement.setAttribute("type","text/css");
styleElement.innerHTML = cssText;
var refNode = element.hasChildNodes() ? element.children[0] : null;
element.insertBefore( styleElement, refNode );
}
}
function svgString2Image( svgString, width, height, format, callback ) {
var format = format ? format : 'png';
var imgsrc = 'data:image/svg+xml;base64,'+ btoa( unescape( encodeURIComponent( svgString ) ) ); // Convert SVG string to data URL
var canvas = document.createElement("canvas");
var context = canvas.getContext("2d");
canvas.width = width;
canvas.height = height;
var image = new Image();
image.onload = function() {
context.clearRect ( 0, 0, width, height );
context.drawImage(image, 0, 0, width, height);
canvas.toBlob( function(blob) {
var filesize = Math.round( blob.length/1024 ) + ' KB';
if ( callback ) callback( blob, filesize );
});
};
image.src = imgsrc;
}
</script>
</html>
@mberhorst
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mberhorst commented Feb 8, 2018 •
edited
Loading

I would recommend to use a single css file for all the chart-relevant styles instead of this complex parsing of the relevant css classes.
With the plain css in hand you have everything you need to render the png and can remove half of the code. Also you can be sure that every css-class is present.

Or use your complete css...I inserted a huge minified css file instead of parsing the relevant classes and had no performance impact. But a reduced css would be cleaner.

@brunojennrich
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great start! thanks!

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