def METHOD_NAME(self):
    magic, header_size = struct.unpack("<II", self.fp.read(8))
    if header_size != 124:
        raise IOError("Unsupported header size %r" % (header_size))
    header_bytes = self.fp.read(header_size - 4)
    if len(header_bytes) != 120:
        raise IOError("Incomplete header: %s bytes" % len(header_bytes))
    header = BytesIO(header_bytes)
    flags, height, width = struct.unpack("<3I", header.read(12))
    self._size = (width, height)
    self.mode = "RGBA"
    pitch, depth, mipmaps = struct.unpack("<3I", header.read(12))
    struct.unpack("<11I", header.read(44))  # reserved
    # pixel format
    pfsize, pfflags = struct.unpack("<2I", header.read(8))
    fourcc = header.read(4)
    bitcount, = struct.unpack("<I", header.read(4))
    masks = struct.unpack("<4I", header.read(16))
    if pfflags & 0x40:
        # DDPF_RGB - Texture contains uncompressed RGB data
        masks = {mask: ["R", "G", "B", "A"][i] for i, mask in enumerate(masks)}
        rawmode = ""
        if bitcount == 32:
            rawmode += masks[0xFF000000]
        rawmode += masks[0xFF0000] + masks[0xFF00] + masks[0xFF]
        self.tile = [("raw", (0, 0) + self.size, 0, (rawmode, 0, 1))]
    else:
        data_start = header_size + 4
        n = 0
        if fourcc == b"DXT1":
            self.pixel_format = "DXT1"
            n = 1
        elif fourcc == b"DXT3":
            self.pixel_format = "DXT3"
            n = 2
        elif fourcc == b"DXT5":
            self.pixel_format = "DXT5"
            n = 3
        elif fourcc == b"DX10":
            data_start += 20
            # ignoring flags which pertain to volume textures and cubemaps
            dxt10 = BytesIO(self.fp.read(20))
            dxgi_format, dimension = struct.unpack("<II", dxt10.read(8))
            if dxgi_format in (DXGI_FORMAT_BC7_TYPELESS, DXGI_FORMAT_BC7_UNORM):
                self.pixel_format = "BC7"
                n = 7
            elif dxgi_format == DXGI_FORMAT_BC7_UNORM_SRGB:
                self.pixel_format = "BC7"
                self.im_info["gamma"] = 1 / 2.2
                n = 7
            else:
                raise NotImplementedError(
                    "Unimplemented DXGI format %d" % (dxgi_format)
                )
        else:
            raise NotImplementedError("Unimplemented pixel format %r" % (fourcc))
        self.tile = [("bcn", (0, 0) + self.size, data_start, (n))]