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"""
Utility functions for handling images.
Requires Pillow as you might imagine.
"""
import struct
import zlib
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, close=close)
return self._dimensions_cache
def get_image_dimensions(file_or_path, close=False):
"""
Returns the (width, height) of an image, given an open file or a path. Set
'close' to True to close the file at the end if it is initially in an open
state.
"""
from PIL import ImageFile as PillowImageFile
p = PillowImageFile.Parser()
if hasattr(file_or_path, 'read'):
file = file_or_path
file_pos = file.tell()
file.seek(0)
else:
file = open(file_or_path, 'rb')
close = True
try:
# Most of the time Pillow only needs a small chunk to parse the image
# and get the dimensions, but with some TIFF files Pillow needs to
# parse the whole file.
chunk_size = 1024
while 1:
data = file.read(chunk_size)
if not data:
break
try:
p.feed(data)
except zlib.error as e:
# ignore zlib complaining on truncated stream, just feed more
# data to parser (ticket #19457).
if e.args[0].startswith("Error -5"):
pass
else:
raise
except struct.error:
# Ignore PIL failing on a too short buffer when reads return
# less bytes than expected. Skip and feed more data to the
# parser (ticket #24544).
pass
if p.image:
return p.image.size
chunk_size *= 2
return (None, None)
finally:
if close:
file.close()
else:
file.seek(file_pos)
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