mirror of
https://github.com/Hopiu/django-imagekit.git
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218 lines
7.1 KiB
Python
218 lines
7.1 KiB
Python
from django.conf import settings
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from hashlib import md5
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import os
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import pickle
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from ..exceptions import UnknownExtensionError
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from ..files import GeneratedImageCacheFile, IKContentFile
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from ..imagecache.backends import get_default_image_cache_backend
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from ..imagecache.strategies import StrategyWrapper
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from ..processors import ProcessorPipeline
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from ..utils import (open_image, extension_to_format, img_to_fobj,
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suggest_extension)
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from ..registry import generator_registry, register
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class BaseImageSpec(object):
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"""
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An object that defines how an new image should be generated from a source
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image.
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"""
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cache_file_storage = None
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"""A Django storage system to use to save a generated cache file."""
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image_cache_backend = None
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"""
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An object responsible for managing the state of cached files. Defaults to an
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instance of ``IMAGEKIT_DEFAULT_IMAGE_CACHE_BACKEND``
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"""
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image_cache_strategy = settings.IMAGEKIT_DEFAULT_IMAGE_CACHE_STRATEGY
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"""
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A dictionary containing callbacks that allow you to customize how and when
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the image cache is validated. Defaults to
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``IMAGEKIT_DEFAULT_SPEC_FIELD_IMAGE_CACHE_STRATEGY``.
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"""
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def __init__(self, **kwargs):
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self.image_cache_backend = self.image_cache_backend or get_default_image_cache_backend()
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self.image_cache_strategy = StrategyWrapper(self.image_cache_strategy)
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def generate(self):
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raise NotImplementedError
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# TODO: I don't like this interface. Is there a standard Python one? pubsub?
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def _handle_source_event(self, event_name, source):
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file = GeneratedImageCacheFile(self)
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self.image_cache_strategy.invoke_callback('on_%s' % event_name, file)
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class ImageSpec(BaseImageSpec):
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"""
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An object that defines how to generate a new image from a source file using
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PIL-based processors. (See :mod:`imagekit.processors`)
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"""
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processors = None
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"""A list of processors to run on the original image."""
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format = None
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"""
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The format of the output file. If not provided, ImageSpecField will try to
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guess the appropriate format based on the extension of the filename and the
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format of the input image.
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"""
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options = None
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"""
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A dictionary that will be passed to PIL's ``Image.save()`` method as keyword
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arguments. Valid options vary between formats, but some examples include
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``quality``, ``optimize``, and ``progressive`` for JPEGs. See the PIL
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documentation for others.
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"""
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autoconvert = True
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"""
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Specifies whether automatic conversion using ``prepare_image()`` should be
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performed prior to saving.
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"""
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def __init__(self, source, **kwargs):
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self.source = source
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self.processors = self.processors or []
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self.kwargs = kwargs
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super(ImageSpec, self).__init__()
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@property
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def cache_file_name(self):
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source_filename = self.source.name
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ext = suggest_extension(source_filename, self.format)
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return os.path.normpath(os.path.join(
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settings.IMAGEKIT_CACHE_DIR,
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os.path.splitext(source_filename)[0],
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'%s%s' % (self.get_hash(), ext)))
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return os.path.join(settings.IMAGEKIT_CACHE_DIR,
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'%s%s' % (hash, ext))
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def get_hash(self):
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return md5(pickle.dumps([
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self.source,
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self.kwargs,
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self.processors,
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self.format,
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self.options,
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self.autoconvert,
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])).hexdigest()
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def generate(self):
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# TODO: Move into a generator base class
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# TODO: Factor out a generate_image function so you can create a generator and only override the PIL.Image creating part. (The tricky part is how to deal with original_format since generator base class won't have one.)
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source = self.source
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filename = self.kwargs.get('filename')
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img = open_image(source)
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original_format = img.format
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# Run the processors
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processors = self.processors
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img = ProcessorPipeline(processors or []).process(img)
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options = dict(self.options or {})
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# Determine the format.
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format = self.format
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if filename and not format:
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# Try to guess the format from the extension.
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extension = os.path.splitext(filename)[1].lower()
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if extension:
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try:
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format = extension_to_format(extension)
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except UnknownExtensionError:
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pass
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format = format or img.format or original_format or 'JPEG'
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imgfile = img_to_fobj(img, format, **options)
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# TODO: Is this the right place to wrap the file? Can we use a mixin instead? Is it even still having the desired effect? Re: #111
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content = IKContentFile(filename, imgfile.read(), format=format)
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return content
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def create_spec_class(class_attrs):
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class DynamicSpecBase(ImageSpec):
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def __reduce__(self):
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try:
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getstate = self.__getstate__
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except AttributeError:
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state = self.__dict__
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else:
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state = getstate()
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return (create_spec, (class_attrs, state))
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return type('DynamicSpec', (DynamicSpecBase,), class_attrs)
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def create_spec(class_attrs, state):
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cls = create_spec_class(class_attrs)
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instance = cls.__new__(cls) # Create an instance without calling the __init__ (which may have required args).
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try:
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setstate = instance.__setstate__
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except AttributeError:
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instance.__dict__ = state
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else:
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setstate(state)
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return instance
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class SpecHost(object):
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"""
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An object that ostensibly has a spec attribute but really delegates to the
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spec registry.
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"""
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def __init__(self, spec=None, spec_id=None, **kwargs):
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spec_attrs = dict((k, v) for k, v in kwargs.items() if v is not None)
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if spec_attrs:
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if spec:
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raise TypeError('You can provide either an image spec or'
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' arguments for the ImageSpec constructor, but not both.')
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else:
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spec = create_spec_class(spec_attrs)
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self._original_spec = spec
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if spec_id:
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self.set_spec_id(spec_id)
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def set_spec_id(self, id):
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"""
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Sets the spec id for this object. Useful for when the id isn't
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known when the instance is constructed (e.g. for ImageSpecFields whose
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generated `spec_id`s are only known when they are contributed to a
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class). If the object was initialized with a spec, it will be registered
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under the provided id.
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"""
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self.spec_id = id
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register.spec(id, self._original_spec)
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def get_spec(self, **kwargs):
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"""
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Look up the spec by the spec id. We do this (instead of storing the
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spec as an attribute) so that users can override apps' specs--without
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having to edit model definitions--simply by registering another spec
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with the same id.
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"""
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if not getattr(self, 'spec_id', None):
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raise Exception('Object %s has no spec id.' % self)
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return generator_registry.get(self.spec_id, **kwargs)
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