Quick script for downloading a bunch of wallpapers from a given array of URLs, in a special resolution.

downloadWallpaper.js

#!/usr/bin/env node

/*
	Quick script for downloading a bunch of wallpapers from a given
	array of URLs, in a special resolution.

	Call script:

		node download.js [pathToUrlFile, resolution, destination]

	Default options:
	{
		urls: "wallpapers.json", 	// Path to JSON file with wallpapers, on the format ' {"urls": ['http://..', 'http://']} '
		resolution: "1440x900", 	// Desired resolution
		destination: "../"				// Desired destination for wallpapers
	}

	By Johan Brook, 2013
	("probably would've taken me shorter time to just download those fucking wallpapers manually")

*/

var exec = require("child_process").exec
var fs = require("fs")

var options = {}
var root = this

// Kick it off
init(process.argv.slice(2))

/*
	Initialization

 */
function init(args) {
	options.urls = args[0] || "wallpapers.json"
	options.resolution = args[1] || "1440x900"
	options.destination = args[2] || "../"

	var wallpapers = JSON.parse(fs.readFileSync(options.urls))

	if(wallpapers && wallpapers.urls) {
		downloadWallpapersFromUrls(wallpapers.urls)
	} else {
		console.error("The file '" + options.urls + "' doesn't exist!")
	}
}

/*
	When all wallpapers are downloaded
 */
function done(nbr) {
	console.log("\n** Done! ** "+ nbr + " wallpapers were downloaded")
}

/*
	Download wallpapers from urls in `urls` param array
 */
function downloadWallpapersFromUrls(urls) {
	_each(urls, downloadWallpaperFromUrl, done)
}


function downloadWallpaperFromUrl(url, callback) {

	parseUrlForResolution(url, options.resolution, function(finalImageUrl, originalUrl) {
		exec('wget -P '+options.destination + " "+finalImageUrl, function(error, stdout, sterr) {
			if(error) {
				callback(error)
			}
			else {
				console.log("Downloading '" + prettyFileName(finalImageUrl) + "' in the resolution "+options.resolution+" ...")
				callback(null)
			}
		})
	})
}

/*
	Parse and return a nice representation of the wallpaper url
 */
function prettyFileName(url) {
	var parts = url.split("/")
	return parts[parts.length - 1]
}

/*
	`resolution` should be on the form <number>x<number>,
	like "1440x900".

	Correct resolution will be appended just before the 
	file type extension in `url`, like:

	http://site.com/picture_1440x900.jpg
	(res: 2560x1440) => http://site.com/picture_2560x1440.jpg
 */
function parseUrlForResolution(url, resolution, callback) {
	callback(url.replace(/(\d+x\d+)/g, resolution), url)
}

/*
	Tools You Don't Have To Care About
-------------
 */

/*
	Special version of Array.forEach
	From https://github.com/caolan/async/blob/master/lib/async.js

	Apply iterator to every element in arr and call callback
	whenever all elements are called.
 */
function _each(arr, iterator, callback) {
   callback = callback || function () {}
   if (!arr.length) {
       return callback()
   }
   var completed = 0
   arr.forEach(function (x) {
       iterator(x, _only_once(function (err) {
           if (err) {
               callback(err);
               callback = function () {}
           }
           else {
               completed += 1
               if (completed >= arr.length) {
                   callback(arr.length)
               }
           }
       }))
   })
}

/*
	Make sure a function fn was called only once
 */
function _only_once(fn) {
  var called = false;
  return function() {
      if (called) throw new Error("Callback was already called.");
      called = true;
      fn.apply(root, arguments);
  }
}

wallpapers.json

{
	"urls" : [
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_155_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_159_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_162_blk_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_179_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_204_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_213_wht_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_46_blk_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_4_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_55_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_57_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_59_blk_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_5_wht_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_91_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_107_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_124_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_13_bob_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_149_red_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_150_wht_1440x900.jpg",
		"http://goodfuckingdesignadvice.com/uploads/wallpaper/1440x900/GFDA_151_wht_1440x900.jpg"
	]
}