Add comparative performance tests using random dimensions

tests/random.js

@@ -0,0 +1,75 @@
+var sharp = require("../index");
+var fs = require("fs");
+var imagemagick = require("imagemagick");
+var gm = require("gm");
+var epeg = require("epeg");
+var async = require("async");
+var assert = require("assert");
+var Benchmark = require("benchmark");
+
+var inputJpg = __dirname + "/2569067123_aca715a2ee_o.jpg"; // http://www.flickr.com/photos/grizdave/2569067123/
+var outputJpg = __dirname + "/output.jpg";
+
+var min = 320;
+var max = 960;
+
+var randomDimension = function() {
+  return Math.random() * (max - min) + min;
+}
+
+new Benchmark.Suite("random").add("imagemagick", {
+	defer: true,
+	fn: function(deferred) {
+		imagemagick.resize({
+			srcPath: inputJpg,
+			dstPath: outputJpg,
+			quality: 0.8,
+			width: randomDimension(),
+			height: randomDimension()
+		}, function(err) {
+			if (err) {
+				throw err;
+			} else {
+				deferred.resolve();
+			}
+		});
+	}
+}).add("gm", {
+	defer: true,
+	fn: function(deferred) {
+		gm(inputJpg).resize(randomDimension(), randomDimension()).quality(80).toBuffer(function (err, buffer) {
+			if (err) {
+				throw err;
+			} else {
+				assert.notStrictEqual(null, buffer);
+				deferred.resolve();
+			}
+		});
+	}
+}).add("epeg", {
+	defer: true,
+	fn: function(deferred) {
+		var image = new epeg.Image({path: inputJpg});
+		var buffer = image.downsize(randomDimension(), randomDimension(), 80).process();
+		assert.notStrictEqual(null, buffer);
+		deferred.resolve();
+	}
+}).add("sharp", {
+	defer: true,
+	fn: function(deferred) {
+		sharp.resize(inputJpg, sharp.buffer.jpeg, randomDimension(), randomDimension(), function(err, buffer) {
+			if (err) {
+				throw err;
+			} else {
+				assert.notStrictEqual(null, buffer);
+				deferred.resolve();
+			}
+		});
+	}
+}).on("cycle", function(event) {
+  console.log(String(event.target));
+}).on("complete", function() {
+  var winner = this.filter("fastest").pluck("name");
+  assert.strictEqual("sharp", String(winner), "sharp was slower than " + winner);
+	console.dir(sharp.cache());
+}).run();