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A wsgi middleware to generate and serve image thumbnails.

Project Description


ìw.thumbs` is used to serve image thumbnail. The thumbnail is cached in a directory and served with paste.fileapp so correct headers (ETag, If-Modified, etc.) are returned.

iw.thumbs is highly configurable but if you use Paste to serve your application you probably only need to read the last part of this documentation.


The Thumb middleware take four arguments:

  • application: the wsgi application to wrap.
  • url_parser: a callable to retrieve the size of the thumbnail and the attending size as a tuple (width, height) Default: iw.thumbs.url.url_parser The default value match urls like /thumbs/100x100/path/to/image.png and return (‘/path/to/image.png’, (100, 100))
  • url_regexp: a regexp passed as argument to the default url_parser. The regexp must have groups named path, width and height. Default: ‘^/+thumbs/+(?P<width>[0-9]{2,3})x(?P<height>[0-9]{2,3})/{0,1}(?P<path>/.+)’
  • image_fetcher: a callable to retrieve the real image path Default: iw.thumbs.image_fetcher The default value return the PATH_INFO so you may override it. This callable is used to retrieve image from file system but you can also use it to retrieve image from other location like proxy, ftp, etc.
  • image_dir: a directory where images are stored. Used by image_fetcher if the default one is used.
  • cache_dir: a path to the directory used to cache thumbnails (required)
  • debug: debug mode. Default: False


Write a method to retrieve your image path from the PATH_INFO:

>>> def image_fetcher(path_info):
...     return os.path.join(package_dir, *path_info.split('/')[1:])

Wrap your application with the middleware:

>>> from iw.thumbs.middleware import Thumbs
>>> app = Thumbs(test_app, image_fetcher=image_fetcher, cache_dir=cache_dir)

Then ask for an image:

>>> environ = {'REQUEST_METHOD':'GET',
...            'PATH_INFO':'/thumbs/50x50/tests/logo.png'}
>>> print app.get_app(environ)
<paste.fileapp.FileApp object at ...>

Override the default url regexp:

>>> regexp = '^/my_thumbs/(?P<width>[0-9]+)x(?P<height>[0-9]+)(?P<path>/.+)'
>>> app = Thumbs(test_app, image_fetcher=image_fetcher, cache_dir=cache_dir,
...              url_regexp=regexp)

>>> environ = {'REQUEST_METHOD':'GET', 'PATH_INFO':'/my_thumbs/50x50/tests/logo.png'}
>>> print app.get_app(environ)
<paste.fileapp.FileApp object at ...>

If the path does not match an image, the test_app is served:

>>> environ = {'REQUEST_METHOD':'GET', 'PATH_INFO':'/index.html'}
>>> print app.get_app(environ)
<function test_app at ...>

Using sizes names

You can use size names:

>>> app = Thumbs(test_app, image_fetcher=image_fetcher, cache_dir=cache_dir,
...              url_regexp='/thumbs/(?P<size>%s)(?P<path>/.*)',
...              url_parser='iw.thumbs.url:size_parser',
...              sizes={'thumb': (100,100), 'large': (600,600)})

>>> environ = {'REQUEST_METHOD':'GET', 'PATH_INFO':'/thumbs/large/tests/logo.png'}
>>> print app.get_app(environ)
<paste.fileapp.FileApp object at ...>

Implementing your own parser

You need a callable who return a callable and the compiled regexp.

Let’s define our strategy with a regexp:

>>> re_thumb = '^/thumbs(?P<path>/.*)'

Then implement it with a parser:

>>> import re
>>> def custom_parser(regexp, **kwargs):
...     regexp = re.compile(regexp)
...     def parser(url):
...         m = regexp.match(url)
...         if m:
...             path ='path')
...             return path, (100, 100)
...     return parser, regexp

Check this work:

>>> app = Thumbs(test_app, image_fetcher=image_fetcher, cache_dir=cache_dir,
...              url_regexp=re_thumb, url_parser=custom_parser)

>>> environ = {'REQUEST_METHOD':'GET', 'PATH_INFO':'/thumbs/tests/logo.png'}
>>> print app.get_app(environ)
<paste.fileapp.FileApp object at ...>


Resize an image file to the specified destination at size:

>>> from iw.thumbs.image import resize
>>> thumbnail = os.path.join(cache_dir, 'thumb.png')
>>> print resize(image_path, thumbnail, size=(50, 50))
>>> os.path.isfile(thumbnail)

Paste factory

The package provide a Paste factory.

Here is a sample configuration:

use = egg:Paste#urlmap
/images = thumbs_app
/ = middlewares

# a standalone application to serve files in image_dir. The application is a
# static application wrapped with the iw.thumbs middleware
use = egg:iw.thumbs
url_regexp = ^/+(?P<width>[0-9]+)x(?P<height>[0-9]+)/{0,1}(?P<path>/.+)
image_dir = %(here)s/images
cache_dir = %(here)s/images_cache

pipeline = thumbs named_thumbs test_app

# an example tho override the default regexp
use = egg:iw.thumbs
url_regexp = ^/+(?P<width>[0-9]+)x(?P<height>[0-9]+)/{0,1}(?P<path>/.+)
image_dir = %(here)s/images
cache_dir = %(here)s/images_cache

# another example using sizes names
use = egg:iw.thumbs
url_regexp = ^/(?P<size>%s)(?P<path>/.+)
url_parser = iw.thumbs.url:size_parser
image_dir = %(here)s/images
cache_dir = %(here)s/images_cache
sizes =
    thumb = 200x200
    large = 600x600

use = egg:Paste#static
document_root = %(here)s/

use = egg:Paste#http
host =
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