A few month ago I've created a middleware to generate and cache images thumbnails. I need this to evaluate the image size from the browser's window on the client side and then get the thumbnail at an url based on this size.

The result is iw.thumbs. The package provide a highly configurable middleware to serve images thumbnails.

The principle is to map an uri to a file system directory. Then if an uri match the specified regexp, a thumbnail is served by the middleware.

For example, with the default configuration, the url http://localhost/thumbs/100x100/image.png will render a thumbnail of /var/mapped_dir/image.png.

There is also a "size" uri parser to use named size and prevent potential DoS attacks.

That what i'm using here, for my blog. I have two size: blog (490x490) and large (750x750). Here the Paste configuration:

[app:thumbs]
use = egg:iw.thumbs
url_regexp = ^/(?P<size>%s)(?P<path>/.+)
url_parser = iw.thumbs.url:size_parser
image_dir = %(here)s/var/rst/images
cache_dir = %(here)s/data/thumbs
sizes =
    blog = 490x490
    large = 750x750

As you can see, the package also provide an application factory in case of you just want to math a specific prefix.

Then I just have to map it in my url mapper section:

[app:main]
use = egg:Paste#urlmap
/thumbs = thumbs
/ = pylons # my pylons application

Another middleware exist to generate thumbnail with a different approach. repoze.bitblt allow you to generate thumbnail from the size specified in your image tag. It also add a secure part to the image url to prevent DoS attacks. I think both package have their place.

What I like with iw.thumbs is that I only need to change a configuration parameter instead of all image tags if the width of my blog column change in the future. The other good point is that you can generate image tags on the client side wich seems not really possible with repoze.bitblt.

But well, both middleware are another good reason to use WSGI applications.

And as an example, here is Alain, the AFPy mascot render with the blog size. If you click on it, you'll get the large size in a popup.

This time it's really winter. When it's cold the only thing i like is geeking at home. So I decide to rewrite my website with a set of WSGI applications.

The first thing done was to initialize a Pylons project for my blog. I got something working after a few hours. Pylons really speed developments.

Then I need a skin. I decide to give a try to Deliverance. Skinning with Deliverance is quite easy. After reading the docs, I've create a layout based on my old html code and a set of rules. Add this to my configuration file:

[filter:deliverance]
use = egg:Deliverance
theme_uri = file:///%(here)s/themes/layout.html
rule_uri = file:///%(here)s/themes/rules.xml

That's it. My Pylons app looks good without any style sheet as you can see ;)

Another part of my website is my projects documentations which are generated by Sphinx and served by a static app. Those pages are now skinned with Deliverance and you can't really know that you browse another application.

I also use Trac to browse my svn repository so I've try to put it in my WSGI stack. Trac now support WSGI except that it do something strange with the output and/or stderr so you'd better not using an error middleware with it else you get a beautiful blank page. You can create a WSGI application with a few lines of code:

# -*- coding: utf-8 -*-
import os
from trac.web.main import dispatch_request
def make_trac(conf, trac_env):
    def application(environ, start_request):
        environ['trac.env_path'] = trac_env
        return dispatch_request(environ, start_request)
    return application

and skin it with Deliverance. Notice that in my case, Trac seems inserting different encoding in the same page so I need to hack it a bit.

The last thing done is to use a ProxyApp to serve and skin my buildbot. Of course, this part is also skinned with Deliverance.

I now have only one process to serve all my python apps so I can use repoze.who to manage authentication for all apps. I have a ldap server, so I've write a small plugin for it. This work perfect, and I'm now able to log in Pylons and Trac.

I'm using Deliverance as a WSGI middleware and it seems a bit different than when you use it as a proxy. I encounter a few bugs. I have to only use XPath to find nodes in the DOM. Other expressions just don't work. You also can't remove nodes. But, well, this seems promising.