image in image (overlay image) with gm (GraphicsMagick) - watermark

Question

I want to put a watermark picture (logo) on my resized pictures as you can see in the code below.
Can somebody help how to put a picture in the right low corner with a opacity of 50%?
var fs = require('fs')
, gm = require('gm');
function walk(currentDirPath, callback) {
var fs = require('fs'), path = require('path');
fs.readdirSync(currentDirPath).forEach(function(name) {
var filePath = path.join(currentDirPath, name);
var stat = fs.statSync(filePath);
if (stat.isFile()) {
callback(filePath, stat);
} else if (stat.isDirectory()) {
walk(filePath, callback);
}
});
}
var inputDir = "/Users/USER/Desktop/src/"
var outputDir = "/Users/USER/Desktop/target/"
walk(inputDir, function(filePath, stat) {
// match filename like IMG_1234.JPG
var filename = filePath.match(/IMG_\d{4}.JPG/gmi).toString();
console.log(filename);
var outputfile = outputDir + filename
var readStream = fs.createReadStream(filePath);
gm(readStream, filename)
.size({bufferStream: true}, function(err, size) {
this.resize(size.width / 2, size.height / 2)
this.write(outputfile, function (err) {
if (!err) console.log('done');
});
});
});

Answer 1

Here is the solution:
.draw(['image Over 0,0 0,0 /Users/USER/Desktop/target/nike-global-diversity-logo.png'])
put this line of code after gm call and before the resizing.