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POProblems serving a binary image passed through stdout with Node
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copied!<p>I'm attempting to create a node server that serves up a png image generated using the node-wkhtml module (basically just a wrapper for the wkhtmltoimage/wkhtmltopdf command line utility). Here's what I have so far:</p> <pre><code>var http = require('http'); var Image = require("node-wkhtml").image(); http.createServer(function (request, response) { new Image({ url: "www.google.com" }).convert (function (err, stdout) { //var theImage = new Buffer (stdout, 'binary'); response.writeHead(200, {'Content-Type' : 'image/png', 'Content-Length' : stdout.length }); response.write (stdout, 'binary'); response.end (); //write out an error, if there is one if (err) console.log (err); }); }).listen(8124); </code></pre> <p>Basically, the module calls the command:</p> <pre><code>wkhtmltoimage www.google.com - </code></pre> <p>which then generates a png image and writes it to the stdout. The amount of data served seems to be correct, but I can't get the browser to display it (nor does it work if I download it as a file). I tried the following command:</p> <pre><code>wkhtmltoimage www.google.com - > download.png </code></pre> <p>and sure enough, download.png was created and contained a snapshot of the google homepage, meaning that the wkhtmltoimage utility is working correctly, and the command works. I'm a beginner at node, so I'm not super familiar how to serve up a binary file like this, can anyone see any glaring issues? Here's the node module code that works the magic:</p> <pre><code>Image.prototype.convert = function(callback) { exec(util.buildCommand(this), {encoding: 'binary', maxBuffer: 10*1024*1024}, callback); } </code></pre> <p>(the buildCommand function just generates the "wkhtmltoimage www.google.com -" command, and I've verified it does this correctly, using node inspector.</p> <p>UPDATE: In case anyone finds this later and is interested, I found the solution. The plugin I was using (node-wkhtml) was not properly handling large buffers, due to the choice of using <code>child-process.exec</code> I changed the plugin code to use <code>child-process.spawn</code> instead, and it worked as desired.</p>

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