39 lines
1.1 KiB
Python
39 lines
1.1 KiB
Python
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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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"""Image header parser for GIF images.
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Note that the GIF format does not support resolution (DPI) information. Both
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horizontal and vertical DPI 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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"""Return |Gif| instance having header properties parsed from GIF image in
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`stream`."""
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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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"""MIME content type for this image, unconditionally `image/gif` for GIF
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images."""
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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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"""Default filename extension, always 'gif' for GIF images."""
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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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