How to read an image from phantomjs stdout in node

问题:

There's probably some detail that I'm missing, because the rasterization script works fine standalone, but I haven't been successful reading its output from NodeJS so far.

Here's the NodeJS part:

var http = require('http');
var qs = require('querystring');
var fs = require('fs');
var spawn = require('child_process').spawn;

var SCRIPT = fs.readFileSync('./script.js', { encoding: 'utf8' });

http.createServer(function (request, response) {
    var body = '';
    request.on('data', function (data) {
        body += data;
    });
    request.on('end', function () {
        var postData = qs.parse(body);
        var phantomOut = '';
        var phantom = spawn('phantomjs');
        phantom.stdout.on('data', function (buf) {
            phantomOut += buf;
        });
        phantom.on('exit', function (code) {
            response.writeHead(200, {
                'Content-Type': 'image/png'
            });
            response.end(phantomOut);
        });
        phantom.stdin.setEncoding('utf8');
        phantom.stdin.write( SCRIPT.replace('(#imageData)', postData.imageData) );
    });
}).listen(1337, '127.0.0.1');

And here's the 'script.js' that is executed by PhantomJS:

var page = require('webpage').create();
page.content = '<img src="(#imageData)">';
window.setTimeout(function () {
    page.render('/dev/stdout', { format: 'png' });
    phantom.exit();
}, 1);

What I'd like to do is to render Base64 encoded image to PNG with phantomjs to stdout, read that image in nodejs and then serve it.

What am I doing wrong?

回答1:

I noticed that you have found a solution. Just for the sake of others who may land here, here is a far easier answer:

PhantomJS:

var base64 = page.renderBase64('PNG');
system.stdout.write(base64);
phantom.exit();

Node (using phantomjs-prebuilt):

childProcess.execFile(binPath, childArgs, function(err, stdout, stderr) {
  var buf = new Buffer(stdout, 'base64');
  fs.writeFile('test.png', buf);
}