var PngQuant = require('pngquant'),
    myPngQuanter = new PngQuant([192, '--quality', '60-80', '--nofs', '-']);

sourceStream.pipe(myPngQuanter).pipe(destinationStream);

var PngQuant = require('pngquant'),
    http = require('http');

http.createServer(function (req, res) {
    if (req.headers['content-type'] === 'image/png') {
        res.writeHead(200, {'Content-Type': 'image/png'});
        req.pipe(new PngQuant([128])).pipe(res);
    } else {
        res.writeHead(400);
        res.end('Feed me a PNG!');
    }
}).listen(1337);