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48 lines
1.2 KiB
Python
48 lines
1.2 KiB
Python
3 weeks ago
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# encoding: utf-8
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from __future__ import absolute_import, division, print_function
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from struct import Struct
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from .constants import MIME_TYPE
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from .image import BaseImageHeader
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class Gif(BaseImageHeader):
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"""
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Image header parser for GIF images. Note that the GIF format does not
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support resolution (DPI) information. Both horizontal and vertical DPI
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default to 72.
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"""
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@classmethod
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def from_stream(cls, stream):
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"""
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Return |Gif| instance having header properties parsed from GIF image
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in *stream*.
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"""
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px_width, px_height = cls._dimensions_from_stream(stream)
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return cls(px_width, px_height, 72, 72)
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@property
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def content_type(self):
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"""
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MIME content type for this image, unconditionally `image/gif` for
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GIF images.
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"""
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return MIME_TYPE.GIF
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@property
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def default_ext(self):
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"""
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Default filename extension, always 'gif' for GIF images.
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"""
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return 'gif'
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@classmethod
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def _dimensions_from_stream(cls, stream):
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stream.seek(6)
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bytes_ = stream.read(4)
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struct = Struct('<HH')
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px_width, px_height = struct.unpack(bytes_)
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return px_width, px_height
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