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EmoteManager/utils/image.py

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# © 20182020 io mintz <io@mintz.cc>
#
# Emote Manager is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# Emote Manager is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with Emote Manager. If not, see <https://www.gnu.org/licenses/>.
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import asyncio
import base64
import contextlib
import functools
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import io
import logging
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import signal
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import sys
import typing
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logger = logging.getLogger(__name__)
try:
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import wand.image
except (ImportError, OSError):
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logger.warn('Failed to import wand.image. Image manipulation functions will be unavailable.')
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else:
import wand.exceptions
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from utils import errors
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def resize_until_small(image_data: io.BytesIO) -> None:
"""If the image_data is bigger than 256KB, resize it until it's not."""
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# It's important that we only attempt to resize the image when we have to,
# ie when it exceeds the Discord limit of 256KiB.
# Apparently some <256KiB images become larger when we attempt to resize them,
# so resizing sometimes does more harm than good.
max_resolution = 128 # pixels
image_size = size(image_data)
if image_size <= 256 * 2**10:
return
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try:
with wand.image.Image(blob=image_data) as original_image:
while True:
logger.debug('image size too big (%s bytes)', image_size)
logger.debug('attempting resize to at most%s*%s pixels', max_resolution, max_resolution)
with original_image.clone() as resized:
resized.transform(resize=f'{max_resolution}x{max_resolution}')
image_size = len(resized.make_blob())
if image_size <= 256 * 2**10 or max_resolution < 32: # don't resize past 256KiB or 32×32
image_data.truncate(0)
image_data.seek(0)
resized.save(file=image_data)
image_data.seek(0)
break
max_resolution //= 2
except wand.exceptions.CoderError:
raise errors.InvalidImageError
def convert_to_gif(image_data: io.BytesIO) -> None:
try:
with wand.image.Image(blob=image_data) as orig, orig.convert('gif') as converted:
# discord tries to stop us from abusing animated gif slots by detecting single frame gifs
# so make it two frames
converted.sequence[0].delay = 0 # show the first frame forever
converted.sequence.append(wand.image.Image(width=1, height=1))
image_data.truncate(0)
image_data.seek(0)
converted.save(file=image_data)
image_data.seek(0)
except wand.exceptions.CoderError:
raise errors.InvalidImageError
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def mime_type_for_image(data):
if data.startswith(b'\x89PNG\r\n\x1a\n'):
return 'image/png'
if data.startswith(b'\xFF\xD8') and data.rstrip(b'\0').endswith(b'\xFF\xD9'):
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return 'image/jpeg'
if data.startswith((b'GIF87a', b'GIF89a')):
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return 'image/gif'
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if data.startswith(b'RIFF') and data[8:12] == b'WEBP':
return 'image/webp'
raise errors.InvalidImageError
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def image_to_base64_url(data):
fmt = 'data:{mime};base64,{data}'
mime = mime_type_for_image(data)
b64 = base64.b64encode(data).decode('ascii')
return fmt.format(mime=mime, data=b64)
def main() -> typing.NoReturn:
"""resize or convert an image from stdin and write the resized or converted version to stdout."""
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import sys
if sys.argv[1] == 'resize':
f = resize_until_small
elif sys.argv[1] == 'convert':
f = convert_to_gif
else:
sys.exit(1)
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data = io.BytesIO(sys.stdin.buffer.read())
try:
f(data)
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except errors.InvalidImageError:
# 2 is used because 1 is already used by python's default error handler
sys.exit(2)
stdout_write = sys.stdout.buffer.write # getattr optimization
while True:
buf = data.read(16 * 1024)
if not buf:
break
stdout_write(buf)
sys.exit(0)
async def process_image_in_subprocess(command_name, image_data: bytes):
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proc = await asyncio.create_subprocess_exec(
sys.executable, '-m', __name__, command_name,
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stdin=asyncio.subprocess.PIPE,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE)
try:
image_data, err = await asyncio.wait_for(proc.communicate(image_data), timeout=float('inf'))
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except asyncio.TimeoutError:
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proc.send_signal(signal.SIGINT)
raise errors.ImageResizeTimeoutError if command_name == 'resize' else errors.ImageConversionTimeoutError
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else:
if proc.returncode == 2:
raise errors.InvalidImageError
if proc.returncode != 0:
raise RuntimeError(err.decode('utf-8') + f'Return code: {proc.returncode}')
return image_data
resize_in_subprocess = functools.partial(process_image_in_subprocess, 'resize')
convert_to_gif_in_subprocess = functools.partial(process_image_in_subprocess, 'convert')
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def size(fp):
"""return the size, in bytes, of the data a file-like object represents"""
with preserve_position(fp):
fp.seek(0, io.SEEK_END)
return fp.tell()
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class preserve_position(contextlib.AbstractContextManager):
def __init__(self, fp):
self.fp = fp
self.old_pos = fp.tell()
def __exit__(self, *excinfo):
self.fp.seek(self.old_pos)
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if __name__ == '__main__':
main()