minus(other) {
        let {_width: w, _height: h, _buffer: b1} = this;
        let b2 = other._buffer;
        Util.need(other._width === w && other._height === h, "Matrix.minus: compatible sizes");

        let newBuffer = new Float64Array(this._buffer.length);
        for (let i = 0; i < newBuffer.length; i++) {
            newBuffer[i] = b1[i] - b2[i];
        }
        return new Matrix(w, h, newBuffer);
    }
Returns the difference from the receiving matrix to the given matrix.
@param {!Matrix} other
@returns {!Matrix}