from dataclasses import dataclass
from typedstruct import LittleEndianStruct, StructType


@dataclass
class BMPHeader(LittleEndianStruct):
    type: int = StructType.uint16()  # magic identifier: 0x4d42
    size: int = StructType.uint32()  # file size in bytes
    reserved1: int = StructType.uint16()  # not used
    reserved2: int = StructType.uint16()  # not used
    offset: int = StructType.uint32()  # image data offset in bytes
    dib_header_size: int = StructType.uint32()  # DIB header size in bytes
    width_px: int = StructType.int32()  # width of the image
    height_px: int = StructType.int32()  # height of the image
    num_planes_px: int = StructType.uint16()  # number of color planes
    bits_per_pixel: int = StructType.uint16()  # bits per pixel
    compression: int = StructType.uint32()  # compression type
    image_size_bytes: int = StructType.uint32()  # compression type
    x_resolution_ppm: int = StructType.int32()  # pixels per meter
    y_resolution_ppm: int = StructType.int32()  # pixels per meter
    num_colors: int = StructType.int32()  # number of colors
    important_colors_colors: int = StructType.int32()  # important colors


with open("some_file.bmp", "rb") as file:
    raw_data = file.read(BMPHeader.get_size())
    bmp_header = BMPHeader.unpack(raw_data)
    assert bmp_header.type == 0x4D42
    print(f"This image is {bmp_header.width_px}x{bmp_header.height_px}")