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cb1a5c9 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | from .constants import MIME_TYPE
from .helpers import LITTLE_ENDIAN, StreamReader
from .image import BaseImageHeader
class Bmp(BaseImageHeader):
"""Image header parser for BMP images."""
@classmethod
def from_stream(cls, stream):
"""Return |Bmp| instance having header properties parsed from the BMP image in
`stream`."""
stream_rdr = StreamReader(stream, LITTLE_ENDIAN)
px_width = stream_rdr.read_long(0x12)
px_height = stream_rdr.read_long(0x16)
horz_px_per_meter = stream_rdr.read_long(0x26)
vert_px_per_meter = stream_rdr.read_long(0x2A)
horz_dpi = cls._dpi(horz_px_per_meter)
vert_dpi = cls._dpi(vert_px_per_meter)
return cls(px_width, px_height, horz_dpi, vert_dpi)
@property
def content_type(self):
"""MIME content type for this image, unconditionally `image/bmp` for BMP
images."""
return MIME_TYPE.BMP
@property
def default_ext(self):
"""Default filename extension, always 'bmp' for BMP images."""
return "bmp"
@staticmethod
def _dpi(px_per_meter):
"""Return the integer pixels per inch from `px_per_meter`, defaulting to 96 if
`px_per_meter` is zero."""
if px_per_meter == 0:
return 96
return int(round(px_per_meter * 0.0254))
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