async def guess_mime(file: File) -> str:
"""Return the file's mimetype, or `application/octet-stream` if unknown."""
if isinstance(file, io.IOBase):
file.seek(0, 0)
elif isinstance(file, AsyncBufferedReader):
await file.seek(0, 0)
try:
first_chunk: bytes
async for first_chunk in async_generator_from_data(file):
break
else:
return "inode/x-empty" # empty file
# TODO: plaintext
mime = filetype.guess_mime(first_chunk)
return mime or (
"image/svg+xml" if await is_svg(file) else
"application/octet-stream"
)
finally:
if isinstance(file, io.IOBase):
file.seek(0, 0)
elif isinstance(file, AsyncBufferedReader):
await file.seek(0, 0)
async def is_svg(file: File) -> bool:
"""Return whether the file is a SVG (`lxml` is used for detection)."""
chunks = [c async for c in async_generator_from_data(file)]
with io.BytesIO(b"".join(chunks)) as file:
try:
_, element = next(xml_etree.iterparse(file, ("start",)))
return element.tag == "{http://www.w3.org/2000/svg}svg"
except (StopIteration, xml_etree.ParseError):
return False
async def generate_thumbnail(
self,
data: UploadData,
is_svg: bool = False,
) -> Tuple[bytes, MatrixImageInfo]:
"""Create a thumbnail from an image, return the bytes and info."""
png_modes = ("1", "L", "P", "RGBA")
data = b"".join([c async for c in async_generator_from_data(data)])
is_svg = await utils.guess_mime(data) == "image/svg+xml"
if is_svg:
svg_width, svg_height = await utils.svg_dimensions(data)
data = cairosvg.svg2png(
bytestring=data,
parent_width=svg_width,
parent_height=svg_height,
)
thumb = PILImage.open(io.BytesIO(data))
small = thumb.width <= 800 and thumb.height <= 600
is_jpg_png = thumb.format in ("JPEG", "PNG")
jpgable_png = thumb.format == "PNG" and thumb.mode not in png_modes
if small and is_jpg_png and not jpgable_png and not is_svg:
raise UneededThumbnail()
if not small:
thumb.thumbnail((800, 600))
with io.BytesIO() as out:
if thumb.mode in png_modes:
thumb.save(out, "PNG", optimize=True)
mime = "image/png"
else:
thumb.convert("RGB").save(out, "JPEG", optimize=True)
mime = "image/jpeg"
thumb_data = out.getvalue()
thumb_size = len(thumb_data)
if thumb_size >= len(data) and is_jpg_png and not is_svg:
raise UneededThumbnail()
info = MatrixImageInfo(thumb.width, thumb.height, mime, thumb_size)
return (thumb_data, info)
async def svg_dimensions(file: File) -> Size:
"""Return the width and height, or viewBox width and height for a SVG.
If these properties are missing (broken file), ``(256, 256)`` is returned.
"""
chunks = [c async for c in async_generator_from_data(file)]
with io.BytesIO(b"".join(chunks)) as file:
attrs = xml_etree.parse(file).getroot().attrib
try:
width = round(float(attrs.get("width", attrs["viewBox"].split()[3])))
except (KeyError, IndexError, ValueError, TypeError):
width = 256
try:
height = round(float(attrs.get("height", attrs["viewBox"].split()[4])))
except (KeyError, IndexError, ValueError, TypeError):
height = 256
return (width, height)
