Picasa Album Downloader roadmap

August 19, 2008 in en, google, java, projects, python

In my first post about Picasa Album Downloader java applet I promised more in-depth technical information about the project.

Project idea came when few of my less computer savvy friends wanted to download all photos from my Picasa Web Album. So far there have been few different ways to do that:

  • install Picasa and use it,
  • install some other software to download photos,
  • go photo-by-photo and download them one-by-one.

None of those methods is very user friendly. Why isn’t there a “Download album as zip archive” link on Picasa? I have a few theories, but that’s probably for another blog post :)

Question is: How to enable users to download Picasa albums easily? Apparently I was not the only one with the idea of creating web service to create zip file for users to download. Fortunately Google provides APIs for most of its services in few languages. More precisely you can access Picasa easily using:

  • .NET
  • Java
  • PHP
  • Python

Since I started learning Python step-by-step few months ago, I thought about using it for the job. Then I realized that I will need hosting for the web service. There are not too many free python hosting services. Those that are free usually have some restrictions.

Even Google provides hosting services using its own App Engine, with support for Python in particular. I created simple prototype python script that was able to download selected album from given user to the chosen output directory. It ran just fine when I was testing it, but stopped working when run inside dev_appserver.py. Reason? Hotlinking.

Picasa Web Album checks referer header and if it doesn’t match one of Google domains, Picasa blocks access to the images. Since App Engine dosn’t allow clearing of referer header, this effectively blocks using full scale images from Picasa in App Engine. So python is out. What else is there?

I don’t have much experience with .NET, and I also don’t think that it would be suitable for web application that is supposed to be free. I already had some experience with PHP and for project like this one, it would probably do the job just fine. There was a problem though…Google Data APIs needs at least PHP 5.14 to work, but hosting services I had at my disposal had lower versions installed.

Status? Python, .NET, PHP, Java. And here we are. The result is a Java applet that enables users to download full Picasa album without installing any software. There is also a project page at Google Code. First version took about 1 day to code. I released it under GPLv3, so if you want to contribute, you are welcome to do so. If you find any bugs or have ideas how to make the applet better, let me know.