AWS lambda convert svg to png - node.js

Question

I would like to use the AWS Lambda service to convert SVG to PNG with the language NodeJS.
In a second time, the SVG will contain text with custom fonts, I want to know how to use external fonts.
Currently i convert SVG to PNG with PHP Here is an example of conversion in PHP:
$im = new Imagick();
$draw = new ImagickDraw();
$im->setFormat('MSVG');
// Open SVG with ImageMagick
$im->readImageBlob($svgParse->asXML());
$im->setImagePage(0, 0, 0, 0);
$im->scaleImage($viewBox['2'],$viewBox['3'], false);
// Add Text with custom FONT
foreach($ListText as $text){
// Set Custom FONT
$draw->setFont(Mage::getBaseDir('media').DS.'font'.DS.$text['font-family'].".ttf");
$draw->setFontSize( $text['font-size'] );
$draw->setFillColor ( $text['fill']);
// Add text in image
$im->annotateImage($draw, $text['x'], $text['y'], 0, $text['text']);
}
/*png settings*/
// FB image
$imFB = clone $im;
$imFB->setFormat('PNG');
$imFB->cropImage(760, 400,0, 0);
$imFB->scaleImage(600,400,1);
// Save
$imFB->writeImage($filename_FB);
$imFB->clear();
$imFB->destroy();
it would be perfect if I can transform the above code for AWS Lambda. I chose NodeJS because I find more examples on web compared to Python and Java but if you control over Python or Java, no problem I change language
code currently on AWS lambda :
var im = require('imagemagick');
var fs = require('fs');
var util = require("util");
var postProcessResource = function(resource, fn) {
var ret = null;
if (resource) {
if (fn) {
ret = fn(resource);
}
try {
fs.unlinkSync(resource);
} catch (err) {
// Ignore
}
}
return ret;
};
exports.handler = function(event, context) {
var operation = event.operation;
delete event.operation;
if (operation) {
console.log('Operation', operation, 'requested');
}
switch (operation) {
case 'ping':
context.succeed('pong');
break;
case 'convert':
var conv = im.convert(['svg:-', 'png:-'])
conv.on('data', function(data) {
//console.log('data');
//console.log(data);
});
conv.on('end', function() {
//console.log('end');
});
conv.stdin.write('<svg height="100%" version="1.1" width="100%" style="overflow: hidden; position: relative;" id="paper" viewBox="0 0 760 890" preserveAspectRatio="xMinYMin"><desc style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">Created with Raphaël 2.1.2</desc><defs style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);"></defs><image x="0" y="0" width="760" height="890" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://camaieu.akria.fr/media/catalog/product/cache/1/image_position_coeur/9df78eab33525d08d6e5fb8d27136e95/3/_/3_1_2.png" id="svg_image" preserveaspectratio="" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);" stroke-width="1" product_id="22"></image><text x="320" y="400" text-anchor="left" font-family="detex" font-size="32px" stroke="none" fill="#fefefe" id="svg_message" stroke-width="1" height="80" width="170" style="font-size: 32px;"><tspan dy="10.6015625" style="-webkit-tap-highlight-color: rgba(0, 0, 0, 0);">zdfazerf</tspan></text></svg>');
conv.stdin.end();
console.log(conv.toString('base64'));
break;
default:
context.fail(new Error('Unrecognized operation "' + operation + '"'));
}
};
The process takes 9s but I do not know retrieve the result, I do not even know what that actually
Example unsuccessfully :
nodejs imagemagick converting svg to png adds a white background, how to keep it transparent?
I am starting on NodeJS and AWS Lambda.
Thx.

Answer 1

Here's what I just got to work for custom fonts on AWS Lambda with pandoc/xelatex. I'd bet you can adapt this technique for your purposes.
I created a fonts directory in my project and placed all of my fonts there. Also in that directory I created a fonts.conf file that looks like this:
<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<dir>/var/task/fonts/</dir>
<cachedir>/tmp/fonts-cache/</cachedir>
<config></config>
</fontconfig>
And then in my (node.js based) handler function before shelling out to call pandoc I set an ENV var to tell fontconfig where to find the fonts.
process.env.FONTCONFIG_PATH='/var/task/fonts'
After doing that I can refer to a font, like Bitter, in my template by name (just Bitter) and then pandoc/xelatex/fontconfig/whatever knows which version of the font to use (like Bitter-Bold.otf vs Bitter-Italic.otf) based on the styling that any bit of text is supposed to have.
I figured this out based on the tips in this project for getting RSVG to work with custom fonts on Lambda: https://github.com/claudiajs/rsvg-convert-aws-lambda-binary/blob/master/README.md#using-custom-fonts