68 lines
2.5 KiB
Python
68 lines
2.5 KiB
Python
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import io
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import logging
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import contextlib
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logger = logging.getLogger(__name__)
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try:
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from wand.image import Image
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except ImportError:
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logger.warn('Failed to import wand.image. Image manipulation functions will be unavailable.')
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from utils import errors
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def resize_until_small(image_data: io.BytesIO):
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"""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,
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# ie when it exceeds the Discord limit of 256KiB.
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# Apparently some <256KiB images become larger when we attempt to resize them,
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# so resizing sometimes does more harm than good.
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max_resolution = 128 # pixels
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image_size = size(image_data)
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while image_size > 256 * 2**10 and max_resolution >= 32: # don't resize past 32x32 or 256KiB
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logger.debug('image size too big (%s bytes)', image_size)
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logger.debug('attempting resize to %s*%s pixels', max_resolution, max_resolution)
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image_data = thumbnail(image_data, (max_resolution, max_resolution))
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image_size = size(image_data)
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max_resolution //= 2
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return image_data
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def size(data: io.BytesIO):
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"""return the size, in bytes, of the data a BytesIO object represents"""
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with preserve_position(data):
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data.seek(0, io.SEEK_END)
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return data.tell()
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def thumbnail(image_data: io.BytesIO, max_size=(128, 128)):
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"""Resize an image in place to no more than max_size pixels, preserving aspect ratio."""
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# Credit to @Liara#0001 (ID 136900814408122368)
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# https://gitlab.com/Pandentia/element-zero/blob/47bc8eeeecc7d353ec66e1ef5235adab98ca9635/element_zero/cogs/emoji.py#L243-247
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image = Image(blob=image_data)
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image.resize(*scale_resolution((image.width, image.height), max_size))
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# we create a new buffer here because there's wand errors otherwise.
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# specific error:
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# MissingDelegateError: no decode delegate for this image format `' @ error/blob.c/BlobToImage/353
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out = io.BytesIO()
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image.save(file=out)
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out.seek(0)
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return out
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def scale_resolution(old_res, new_res):
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# https://stackoverflow.com/a/6565988
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"""Resize a resolution, preserving aspect ratio. Returned w,h will be <= new_res"""
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old_width, old_height = old_res
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new_width, new_height = new_res
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old_ratio = old_width / old_height
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new_ratio = new_width / new_height
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if new_ratio > old_ratio:
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return (old_width * new_height//old_height, new_height)
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return new_width, old_height * new_width//old_width
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class preserve_position(contextlib.AbstractContextManager):
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def __init__(self, fp):
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self.fp = fp
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self.old_pos = fp.tell()
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def __exit__(self, *excinfo):
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self.fp.seek(self.old_pos)
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