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57 lines
1.5 KiB
57 lines
1.5 KiB
# encoding: utf-8
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from __future__ import absolute_import, division, print_function
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from .constants import MIME_TYPE
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from .helpers import LITTLE_ENDIAN, StreamReader
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from .image import BaseImageHeader
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class Bmp(BaseImageHeader):
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"""
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Image header parser for BMP images
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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 |Bmp| instance having header properties parsed from the BMP
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image in *stream*.
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"""
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stream_rdr = StreamReader(stream, LITTLE_ENDIAN)
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px_width = stream_rdr.read_long(0x12)
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px_height = stream_rdr.read_long(0x16)
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horz_px_per_meter = stream_rdr.read_long(0x26)
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vert_px_per_meter = stream_rdr.read_long(0x2A)
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horz_dpi = cls._dpi(horz_px_per_meter)
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vert_dpi = cls._dpi(vert_px_per_meter)
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return cls(px_width, px_height, horz_dpi, vert_dpi)
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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/bmp` for
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BMP images.
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"""
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return MIME_TYPE.BMP
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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 'bmp' for BMP images.
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"""
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return 'bmp'
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@staticmethod
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def _dpi(px_per_meter):
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"""
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Return the integer pixels per inch from *px_per_meter*, defaulting to
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96 if *px_per_meter* is zero.
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"""
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if px_per_meter == 0:
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return 96
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return int(round(px_per_meter * 0.0254))
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