222 lines
8.2 KiB
Python
222 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 type(image_orientation) is 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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