PDF to PNG with Node.js and GhostScript

pdf2png.js

var exec = require('child_process').exec;
var fs = require('fs');
var util = require('util');
var http = require('http');
var url = require('url');
var PDFDocument = require('pdfkit'); // http://pdfkit.org/


http.createServer(function (req, res) {
	
	// Parse URL to get a filename
	
	var urlObj = url.parse(req.url, true);
	var filename = urlObj.query["filename"];
	
	
	// Create a PDF with PDFKit
	
	var doc = new PDFDocument({
		size: 'A4',
		layout: 'portrait'
	});
	
	doc.fontSize(22);
	doc.text('Your file: '+filename+'.pdf', 20, 20);
	doc.fontSize(16);
	doc.text('Was created successfully if you see this.', 20, 30);
	
	doc.save();
	doc.moveTo(100, 150);
	doc.lineTo(100, 250);
	doc.lineTo(200, 250);
	doc.fill("#FF3300");
	doc.restore();
	
	doc.write("./output/"+filename+".pdf");
	
	
	// Render PNG with GhostScript
	
	exec("/usr/bin/gs -dQUIET -dPARANOIDSAFER -dBATCH -dNOPAUSE -dNOPROMPT -sDEVICE=png16m -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -r72 -dFirstPage=1 -dLastPage=1 -sOutputFile=./output/"+filename+".png ./output/"+filename+".pdf", function (error, stdout, stderr) {
		
		if ( error !== null ) {
			console.log(error);
		}
		else {
			var img = fs.readFileSync('./output/'+filename+'.png');
			res.writeHead(200, {'Content-Type': 'image/png' });
			res.end(img, 'binary');
			console.log('Created PNG: '+filename+'.png');
		}
	});
	
}).listen(3000);

console.log('Server running.');

is there a way to write the resulting png directly to a variable without the output file?