"""

Utility functions for handling images.

Requires PIL, as you might imagine.

"""

from django.core.files import File

class ImageFile(File):

    """

    A mixin for use alongside django.core.files.base.File, which provides

    additional features for dealing with images.

    """

    def _get_width(self):

        return self._get_image_dimensions()[0]

    width = property(_get_width)

    def _get_height(self):

        return self._get_image_dimensions()[1]

    height = property(_get_height)

    def _get_image_dimensions(self):

        if not hasattr(self, '_dimensions_cache'):

            close = self.closed

            self.open()

            self._dimensions_cache = get_image_dimensions(self)

            if close:

                self.close()

        return self._dimensions_cache

def get_image_dimensions(file_or_path):

    """Returns the (width, height) of an image, given an open file or a path."""

    p = PILImageFile.Parser()

    close = False

    if hasattr(file_or_path, 'read'):

        file = file_or_path

    else:

        file = open(file_or_path, 'rb')

        close = True

    try:

        while 1:

            data = file.read(1024)

            if not data:

                break

            p.feed(data)

            if p.image:

                return p.image.size

        return None

    finally:

        if close:

            file.close()