picasa.js

/* npm install request */
var user = null;
var album = null;
var authkey = null;
var downloadDir = './download/{user}-{album}/';

var args = process.argv.slice(2);

if(args.length >= 1 && args[0].substr(0, 4) === 'http'){
	user = args[0].substr(args[0].indexOf('.com/') + 5).split('/')[0];
	album = args[0].substr(args[0].indexOf(user + '/') + user.length + 1).split('?')[0];
	authkey = args[0].substr(args[0].indexOf('authkey=') + 8).split('&')[0];
	downloadDir = downloadDir.replace('{album}', album);
	
	var https = require('https');
	var htmlReq = https.get(args[0], function(res) {
		var albumHTML = '';

		res.on('data', function(chunk) {
			albumHTML += chunk;
		});

		res.on('end', function() {
			album = albumHTML.substr(albumHTML.indexOf('var _album = {id:\'') + 18).split('\'')[0];

			download();
		});
	});

	if(args.length >= 2)
		downloadDir = args[1];
}else{
	if(args.length >= 1)
		user = args[0];

	if(args.length >= 2)
		album = args[1];

	if(args.length >= 3)
		authkey = args[2];

	if(args.length >= 4)
		downloadDir = args[3];

	if(user === null || album === null)
		console.error('No user or album given.');
	else
		download();
}

var download = function(){
	downloadDir = downloadDir.replace('{user}', user).replace('{album}', album);

	var url = 'https://picasaweb.google.com/data/feed/base/user/' + user + '/albumid/' + album + '?alt=json&kind=photo' + (authkey != null ? '&authkey=' + authkey : '');
	var https = require('https');
	var req = https.get(url, function(res) {
		var json = '';

		res.on('data', function(chunk) {
			json += chunk;
		});

		res.on('end', function() {
			_searchPhotos(JSON.parse(json));
		});
	});
}

var _searchPhotos = function (result){
	result.feed.entry.forEach(function (item){
		var url = item.content.src;
		url = url.replace("%20", " ");
		url = url.replace("%20", " ");
		url = url.replace("%22", "\"");
		url = url.replace("%27", "'");

		var index = url.lastIndexOf('/');
		url = url.substr(0, index) + '/d' + url.substr(index);

		_downloadPhoto(url);
	});
};

var _downloadPhoto = function (url){
	var fs = require('fs');
	var request = require('request');

	if(!fs.existsSync(downloadDir))
		fs.mkdirSync(downloadDir);

	request.head(url, function(err, res, body){
		var fileName = url.substr(url.lastIndexOf('/') + 1);
		console.log('Downloaded ' + fileName);

		request(url).pipe(fs.createWriteStream(downloadDir + fileName));
	});
}

usage.md

npm install request && node ./picasa.js [url]