public function getTopLeftOnBit() : ?array
    {
        $bitsOffset = 0;

        while ($bitsOffset < count($this->bits) && 0 === $this->bits[$bitsOffset]) {
            ++$bitsOffset;
        }

        if (count($this->bits) === $bitsOffset) {
            return null;
        }

        $x = intdiv($bitsOffset, $this->rowSize);
        $y = ($bitsOffset % $this->rowSize) << 5;

        $bits = $this->bits[$bitsOffset];
        $bit = 0;

        while (0 === ($bits << (31 - $bit))) {
            ++$bit;
        }

        $x += $bit;

        return [$x, $y];
    }