image transformation is a common task for web developpers.
i've created a package to make them stop reinventing the wheel each time they need to resize an image or something else.
this package provides an IImageTransformer adapter to adapt an IImage.
IImageTransformer use a named IImageLibrary utility to transform the image.
i've already implemented an ImagingLibrary for PIL and an ImageMagickLibrary for ImageMagick but you can implements, register and then use your own IImageLibrary.
the default IImageLibrary used by IImageTransformer is configured via zcml.
this way you don't have to take care which library is used when you resize/rotate your image.
i'd realy like to see this in the zope3 core or at least in a z3c/zf package.
my package is named imagelib and is located in lib/python actualy.
i'm sure my code isn't perfect but it's a good starting point for you guys to implement this.
i don't have write access to the zope repository so if you're interested in this package, i will send it to someone with write access.
i join my doc test file to this email.
regards,
--
Gael
========================= Image library interface. =========================
This package provides a set of utilities and adapters
to implements some image libraries (python-imaging (PIL)
and ImageMagick) functionalities.
Image is adaptable with IReadFile and IWriteFile::
>>> from zope.configuration import xmlconfig
>>> context = xmlconfig.string("""
... <configure
... xmlns='http://namespaces.zope.org/zope'
... >
... <include package="zope.app.component" file="meta.zcml" />
... <adapter
... for="zope.app.file.interfaces.IFile"
... provides="zope.app.filerepresentation.interfaces.IReadFile"
... factory="zope.app.file.file.FileReadFile"
... />
... <adapter
... for="zope.app.file.interfaces.IFile"
... provides="zope.app.filerepresentation.interfaces.IWriteFile"
... factory="zope.app.file.file.FileWriteFile"
... />
... <include package="imagelib" file="configure.zcml" />
... </configure>
... """)
We can create an Image object and use the transformer to resize it.
We don't have to take care of which image library is used::
>>> import imagelib
>>> from imagelib.tests import getTestImage
>>> from imagelib.interfaces import IImageTransformer
>>> image = getTestImage()
>>> image.getImageSize()
(145, 42)
>>> transformer = IImageTransformer(image)
>>> transformer.resize((100,100))
>>> size = image.getImageSize()
>>> 100 in size
True
We can also rotate the image::
>>> image = getTestImage()
>>> image.getImageSize()
(145, 42)
>>> transformer = IImageTransformer(image)
>>> transformer.rotate(90)
>>> image.getImageSize()
(42, 145)
We can work on a copy of the original image::
>>> transformer2 = transformer.copy()
>>> image is transformer.getObject()
True
>>> image is transformer2.getObject()
False
ImageTransformer also implement IReadFile::
>>> from zope.app.filerepresentation.interfaces import IReadFile
>>> IReadFile.providedBy(transformer)
True
>>> image.data == transformer.read()
True
PIL is used as default image library but
we can force which librairie is used::
>>> image = getTestImage()
>>> image.getImageSize()
(145, 42)
>>> transformer = IImageTransformer(image)
>>> transformer.library
u'pil'
>>> transformer.library = 'im'
>>> transformer.library
u'im'
>>> transformer.rotate(90)
>>> image.getImageSize()
(42, 145)
We can also change the default library via a zcml directive::
>>> context = xmlconfig.string("""
... <configure
... xmlns='http://namespaces.zope.org/zope'
... >
... <imagelibrary
... name="im"
... default="True"
... />
... </configure>
... """,context)
>>> transformer = IImageTransformer(image)
>>> transformer.library
u'im'
We can't use a non-exist library::
>>> transformer.library = 'mylib'
Traceback (most recent call last):
...
ComponentLookupError: 'No utility named mylib.'
But we can register a new library via zcml::
>>> context = xmlconfig.string("""
... <configure
... xmlns='http://namespaces.zope.org/zope'
... >
... <imagelibrary
... name="mylib"
... factory="imagelib.tests.MyImageLibrary"
... />
... </configure>
... """,context)
Now we can use it::
>>> image = getTestImage()
>>> transformer = IImageTransformer(image)
>>> transformer.library = 'mylib'
>>> transformer.library
u'mylib'
>>> transformer.resize((100,100))
But, hum, our custom library don't resize anything::
>>> image.getImageSize()
(145, 42)
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