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Versions: 11
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Contents
# Based on https://en.wikipedia.org/wiki/BMP_file_format
class FormatParser::BMPParser
include FormatParser::IOUtils
VALID_BMP = 'BM'
PIXEL_ARRAY_OFFSET = 54
def call(io)
io = FormatParser::IOConstraint.new(io)
magic_number, _file_size, _reserved1, _reserved2, dib_header_location = safe_read(io, 14).unpack('A2Vv2V')
return unless VALID_BMP == magic_number
return unless dib_header_location == PIXEL_ARRAY_OFFSET
dib_header = safe_read(io, 40)
_header_size, width, height, _planes, _bits_per_pixel,
_compression_method, _image_size, horizontal_res,
vertical_res, _n_colors, _i_colors = dib_header.unpack('Vl<2v2V2l<2V2')
# There are cases where the height might by negative indicating the data
# is ordered from top to bottom instead of bottom to top
# http://www.dragonwins.com/domains/getteched/bmp/bmpfileformat.htm#The%20Image%20Header
data_order = height < 0 ? :inverse : :normal
FormatParser::Image.new(
format: :bmp,
width_px: width,
height_px: height.abs,
color_mode: :rgb,
intrinsics: {
vertical_resolution: vertical_res,
horizontal_resolution: horizontal_res,
data_order: data_order
}
)
end
FormatParser.register_parser self, natures: :image, formats: :bmp
end
Version data entries
11 entries across 11 versions & 1 rubygems