Using GM to rotate and brighten image

file-generation.js

'use strict'

var gm = require('gm');

// rotate
function rotate(file, out, callback) {
	var written = 0, data = [];
	for (var i = 10; i < 360; i = i + 10) {
		var fn = out + file + '_r' + i;
		gm(file).rotate('white', i).write(fn, function (err) {
			if (!err) data.push(fn);
			if (++written === 35) callback(null, data);
		});
	}
}

// brighten
function brighten(file, out, callback) {
	var written = 0, data = [];
	for (var i = 10; i < 200; i = i + 10) {
		var fn = out + file + '_b' + i;
		gm(file).modulate(i).write(fn, function (err) {
			if (!err) data.push(fn);
			if (++written === 19) callback(null, data);
		});
	}	
}

rotate('logo', './tmp/', function (err, result) {
	if (err) console.log('error', err);
	else console.log('result', result);
});

brighten('logo', './tmp/', function (err, result) {
	if (err) console.log('error', err);
	else console.log('result', result);
});