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"""Helper to probe basic image information: dimensions and format."""
from __future__ import annotations
import enum
import re
import warnings
from collections.abc import Generator, Mapping
from contextlib import ExitStack, contextmanager, suppress
from pathlib import Path
from typing import TYPE_CHECKING, BinaryIO, Final, NamedTuple, TypeAlias
from xml.etree import ElementTree as etree
import PIL.Image
from ._compat import ExifTags, UnidentifiedImageError
if TYPE_CHECKING:
from typing import Literal
from _typeshed import SupportsRead
class SvgImageInfo(NamedTuple):
format: Literal["svg"] = "svg"
width: float | None = None
height: float | None = None
class PILImageInfo(NamedTuple):
format: str
width: int
height: int
class UnknownImageInfo(NamedTuple):
format: None = None
width: None = None
height: None = None
ImageInfo: TypeAlias = PILImageInfo | SvgImageInfo | UnknownImageInfo
class TiffOrientation(enum.IntEnum):
"""The possible values of the "Exif Orientation" tag."""
TOPLEFT = 1
TOPRIGHT = 2
BOTRIGHT = 3
BOTLEFT = 4
LEFTTOP = 5
RIGHTTOP = 6
RIGHTBOT = 7
LEFTBOT = 8
def __init__(self, value: int):
# True if orientation implies width and height are transposed
self.is_transposed = value in {5, 6, 7, 8}
def get_image_orientation(image: PIL.Image.Image) -> TiffOrientation:
"""Deduce the orientation of the image.
Notes
-----
Note that browsers only seem to respect the "Exif" Orientation tag for JPEG images
(and probably TIFF images). In particular, it is `typically ignored`__ by browsers
when displaying PNG, WEBP and AVIF files (though AVIF files have their own way of
indicating orientation — the "irot" and "imir" properties — which are respected.)
__ https://zpl.fi/exif-orientation-in-different-formats/
Exif information can be stored in PNG files, however the `spec for Exif in PNG`__
does state that the Exif information should be considered "historical", under the
assumption that it was probably copied directly from the source image (where it was
written by, e.g., the camera). It implies that the "unsafe-to-copy" Exif information
(e.g. orientation, size) should be ignored.
__ https://ftp-osl.osuosl.org/pub/libpng/documents/proposals/eXIf/png-proposed-eXIf-chunk-2017-06-15.html
Prior to Lektor 3.4, Lektor's ``get_image_info`` only checked the orientation for
JPEG images (transposing width↔height when appropriate). The ``-auto-orient``
option to ImageMagick's ``convert`` appears to ignore Exif Orientation in PNG files,
too.
Finally, note that reading Exif information from PNG files using Pillow is a slow
operation. It seems to require loading and decoding the full image. (Loading Exif
information from JPEG files does not require decoding the image, so is much
quicker.)
For all of these reasons, we only check the Exif Orientation tag for JPEGs.
""" # pylint: disable=line-too-long
if image.format != "JPEG":
return TiffOrientation.TOPLEFT
exif = image.getexif()
try:
orientation = exif[ExifTags.Base.Orientation]
return TiffOrientation(orientation)
except (ValueError, LookupError):
return TiffOrientation.TOPLEFT
def _parse_svg_units_px(length: str) -> float | None:
match = re.match(r"\d+(?: \.\d* )? (?= (?: \s*px )? \Z)", length.strip(), re.VERBOSE)
if match:
return float(match.group())
return None
class BadSvgFile(Exception):
"""Exception raised when SVG file can not be parsed."""
def _get_svg_info(
source: str | Path | SupportsRead[bytes],
) -> SvgImageInfo | UnknownImageInfo:
try:
_, svg = next(etree.iterparse(source, events=["start"]))
except (etree.ParseError, StopIteration) as exc:
raise BadSvgFile("can not parse SVG file") from exc
if svg.tag != "{http://www.w3.org/2000/svg}svg":
raise BadSvgFile("unknown tag in SVG file")
width = _parse_svg_units_px(svg.attrib.get("width", ""))
height = _parse_svg_units_px(svg.attrib.get("height", ""))
return SvgImageInfo("svg", width, height)
# Mapping from PIL format to Lektor format
_LEKTOR_FORMATS: Final[Mapping[str, str]] = {
"PNG": "png",
"GIF": "gif",
"JPEG": "jpeg",
}
def _PIL_image_info(
image: PIL.Image.Image,
) -> PILImageInfo | UnknownImageInfo:
"""Determine image format and dimensions for PIL Image"""
assert image.format is not None
try:
lektor_fmt = _LEKTOR_FORMATS[image.format]
except LookupError:
return UnknownImageInfo()
width = image.width
height = image.height
orientation = get_image_orientation(image)
if orientation.is_transposed:
width, height = height, width
return PILImageInfo(lektor_fmt, width, height)
@contextmanager
def _save_position(fp: BinaryIO) -> Generator[BinaryIO]:
position = fp.tell()
try:
yield fp
finally:
fp.seek(position)
def get_image_info(source: str | Path | BinaryIO) -> ImageInfo:
"""Determine type and dimensions of an image file."""
with suppress(UnidentifiedImageError), ExitStack() as stack:
if not isinstance(source, (str, Path)):
warnings.warn(
"Passing a file object to 'get_image_info' is deprecated "
"since version 3.4.0. Pass a file path instead.",
DeprecationWarning,
stacklevel=2,
)
stack.enter_context(_save_position(source))
image = stack.enter_context(PIL.Image.open(source))
return _PIL_image_info(image)
with suppress(BadSvgFile), ExitStack() as stack:
if not isinstance(source, (str, Path)):
stack.enter_context(_save_position(source))
return _get_svg_info(source)
return UnknownImageInfo()
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