iw.thumbs 1.2

A wsgi middleware to generate and serve image thumbnails.

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.

Usage

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

Example

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 = m.group('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 ...>

Utils

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))

/..._cache/thumb.png >>> os.path.isfile(thumbnail) True

Paste factory

The package provide a Paste factory.

Here is a sample configuration:

[app:main]

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 [app:thumbs_app] 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:middlewares] pipeline = thumbs named_thumbs test_app

# an example tho override the default regexp [filter:thumbs] 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 [filter:named_thumbs] 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

[app:test_app] use = egg:Paste#static document_root = %(here)s/

[server:main] use = egg:Paste#http host = 0.0.0.0