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d8cc86eff4
Remove type hints from comments which have been added as Python type hints. This helps avoid drift between comments and reality, as well as removing redundant information. Also adds some missing type hints which were simple to fill in.
223 lines
8.2 KiB
Python
223 lines
8.2 KiB
Python
# Copyright 2014-2016 OpenMarket Ltd
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# Copyright 2020-2021 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from io import BytesIO
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from types import TracebackType
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from typing import Optional, Tuple, Type
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from PIL import Image
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logger = logging.getLogger(__name__)
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EXIF_ORIENTATION_TAG = 0x0112
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EXIF_TRANSPOSE_MAPPINGS = {
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2: Image.FLIP_LEFT_RIGHT,
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3: Image.ROTATE_180,
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4: Image.FLIP_TOP_BOTTOM,
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5: Image.TRANSPOSE,
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6: Image.ROTATE_270,
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7: Image.TRANSVERSE,
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8: Image.ROTATE_90,
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}
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class ThumbnailError(Exception):
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"""An error occurred generating a thumbnail."""
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class Thumbnailer:
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FORMATS = {"image/jpeg": "JPEG", "image/png": "PNG"}
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@staticmethod
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def set_limits(max_image_pixels: int) -> None:
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Image.MAX_IMAGE_PIXELS = max_image_pixels
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def __init__(self, input_path: str):
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# Have we closed the image?
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self._closed = False
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try:
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self.image = Image.open(input_path)
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except OSError as e:
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# If an error occurs opening the image, a thumbnail won't be able to
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# be generated.
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raise ThumbnailError from e
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except Image.DecompressionBombError as e:
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# If an image decompression bomb error occurs opening the image,
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# then the image exceeds the pixel limit and a thumbnail won't
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# be able to be generated.
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raise ThumbnailError from e
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self.width, self.height = self.image.size
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self.transpose_method = None
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try:
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# We don't use ImageOps.exif_transpose since it crashes with big EXIF
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#
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# Ignore safety: Pillow seems to acknowledge that this method is
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# "private, experimental, but generally widely used". Pillow 6
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# includes a public getexif() method (no underscore) that we might
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# consider using instead when we can bump that dependency.
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#
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# At the time of writing, Debian buster (currently oldstable)
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# provides version 5.4.1. It's expected to EOL in mid-2022, see
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# https://wiki.debian.org/DebianReleases#Production_Releases
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image_exif = self.image._getexif() # type: ignore
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if image_exif is not None:
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image_orientation = image_exif.get(EXIF_ORIENTATION_TAG)
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assert isinstance(image_orientation, int)
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self.transpose_method = EXIF_TRANSPOSE_MAPPINGS.get(image_orientation)
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except Exception as e:
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# A lot of parsing errors can happen when parsing EXIF
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logger.info("Error parsing image EXIF information: %s", e)
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def transpose(self) -> Tuple[int, int]:
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"""Transpose the image using its EXIF Orientation tag
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Returns:
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A tuple containing the new image size in pixels as (width, height).
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"""
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if self.transpose_method is not None:
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# Safety: `transpose` takes an int rather than e.g. an IntEnum.
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# self.transpose_method is set above to be a value in
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# EXIF_TRANSPOSE_MAPPINGS, and that only contains correct values.
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with self.image:
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self.image = self.image.transpose(self.transpose_method) # type: ignore[arg-type]
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self.width, self.height = self.image.size
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self.transpose_method = None
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# We don't need EXIF any more
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self.image.info["exif"] = None
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return self.image.size
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def aspect(self, max_width: int, max_height: int) -> Tuple[int, int]:
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"""Calculate the largest size that preserves aspect ratio which
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fits within the given rectangle::
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(w_in / h_in) = (w_out / h_out)
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w_out = max(min(w_max, h_max * (w_in / h_in)), 1)
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h_out = max(min(h_max, w_max * (h_in / w_in)), 1)
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Args:
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max_width: The largest possible width.
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max_height: The largest possible height.
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"""
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if max_width * self.height < max_height * self.width:
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return max_width, max((max_width * self.height) // self.width, 1)
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else:
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return max((max_height * self.width) // self.height, 1), max_height
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def _resize(self, width: int, height: int) -> Image.Image:
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# 1-bit or 8-bit color palette images need converting to RGB
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# otherwise they will be scaled using nearest neighbour which
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# looks awful.
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#
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# If the image has transparency, use RGBA instead.
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if self.image.mode in ["1", "L", "P"]:
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if self.image.info.get("transparency", None) is not None:
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with self.image:
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self.image = self.image.convert("RGBA")
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else:
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with self.image:
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self.image = self.image.convert("RGB")
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return self.image.resize((width, height), Image.ANTIALIAS)
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def scale(self, width: int, height: int, output_type: str) -> BytesIO:
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"""Rescales the image to the given dimensions.
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Returns:
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The bytes of the encoded image ready to be written to disk
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"""
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with self._resize(width, height) as scaled:
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return self._encode_image(scaled, output_type)
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def crop(self, width: int, height: int, output_type: str) -> BytesIO:
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"""Rescales and crops the image to the given dimensions preserving
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aspect::
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(w_in / h_in) = (w_scaled / h_scaled)
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w_scaled = max(w_out, h_out * (w_in / h_in))
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h_scaled = max(h_out, w_out * (h_in / w_in))
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Args:
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max_width: The largest possible width.
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max_height: The largest possible height.
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Returns:
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The bytes of the encoded image ready to be written to disk
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"""
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if width * self.height > height * self.width:
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scaled_width = width
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scaled_height = (width * self.height) // self.width
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crop_top = (scaled_height - height) // 2
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crop_bottom = height + crop_top
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crop = (0, crop_top, width, crop_bottom)
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else:
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scaled_width = (height * self.width) // self.height
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scaled_height = height
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crop_left = (scaled_width - width) // 2
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crop_right = width + crop_left
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crop = (crop_left, 0, crop_right, height)
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with self._resize(scaled_width, scaled_height) as scaled_image:
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with scaled_image.crop(crop) as cropped:
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return self._encode_image(cropped, output_type)
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def _encode_image(self, output_image: Image.Image, output_type: str) -> BytesIO:
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output_bytes_io = BytesIO()
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fmt = self.FORMATS[output_type]
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if fmt == "JPEG":
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output_image = output_image.convert("RGB")
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output_image.save(output_bytes_io, fmt, quality=80)
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return output_bytes_io
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def close(self) -> None:
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"""Closes the underlying image file.
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Once closed no other functions can be called.
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Can be called multiple times.
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"""
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if self._closed:
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return
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self._closed = True
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# Since we run this on the finalizer then we need to handle `__init__`
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# raising an exception before it can define `self.image`.
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image = getattr(self, "image", None)
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if image is None:
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return
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image.close()
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def __enter__(self) -> "Thumbnailer":
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"""Make `Thumbnailer` a context manager that calls `close` on
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`__exit__`.
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"""
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return self
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def __exit__(
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self,
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type: Optional[Type[BaseException]],
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value: Optional[BaseException],
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traceback: Optional[TracebackType],
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) -> None:
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self.close()
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def __del__(self) -> None:
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# Make sure we actually do close the image, rather than leak data.
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self.close()
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