Return image data from open file as numpy array.

def _read_data(self, fh, byteorder='>'):
        """Return image data from open file as numpy array."""
        fh.seek(len(self.header))
        data = fh.read()
        dtype = 'u1' if self.maxval < 256 else byteorder + 'u2'
        depth = 1 if self.magicnum == b"P7 332" else self.depth
        shape = [-1, self.height, self.width, depth]
        size = numpy.prod(shape[1:])
        if self.magicnum in b"P1P2P3":
            data = numpy.array(data.split(None, size)[:size], dtype)
            data = data.reshape(shape)
        elif self.maxval == 1:
            shape[2] = int(math.ceil(self.width / 8))
            data = numpy.frombuffer(data, dtype).reshape(shape)
            data = numpy.unpackbits(data, axis=-2)[:, :, :self.width, :]
        else:
            data = numpy.frombuffer(data, dtype)
            data = data[:size * (data.size // size)].reshape(shape)
        if data.shape[0] < 2:
            data = data.reshape(data.shape[1:])
        if data.shape[-1] < 2:
            data = data.reshape(data.shape[:-1])
        if self.magicnum == b"P7 332":
            rgb332 = numpy.array(list(numpy.ndindex(8, 8, 4)), numpy.uint8)
            rgb332 *= [36, 36, 85]
            data = numpy.take(rgb332, data, axis=0)
        return data