cell(col, row) {
        if (col < 0 || row < 0 || col >= this._width || row >= this._height) {
            throw new DetailedError("Cell out of range", {col, row, width: this._width, height: this._height});
        }
        let i = (this._width*row + col)*2;
        return new Complex(this._buffer[i], this._buffer[i + 1]);
    }
@param {int} col
@param {int} row
@returns {!Complex}