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"""

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    State for thumbnails; derivates of Images

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"""

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import filesystem

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import PIL.Image

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class Thumbnail (filesystem.File) :

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    """

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        A Thumbnail is a derivate of an Image, usually resized to some other size.

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    """

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    def __init__ (self, image, subdir, size) :

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        """

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            Initialize to link against the given `image`.

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            `subdir` specifies the directory to store this thumbnail in.

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            `size` determines the target resolution of the output thumbnail.

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        """

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        # our file path

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        # XXX: this should be the binary fsname, not name

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        super(Thumbnail, self).__init__(subdir.subnode(image.name))

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        # store

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        self.image = image

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        self.size = size

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    def stale (self) :

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        """

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            Tests if this thumbnail is stale

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        """

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        return self.older_than(self.image)

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    def update (self) :

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        """

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            Render new output thumbnail

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        """

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        # load a copy of the PIL.Image, as .thumbnail mutates it

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        thumb = self.image.pil_image.copy()

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        # resample to given size

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        thumb.thumbnail(self.size, resample=True)

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        # and write out

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        thumb.save(self.path)

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