传入两坐标点，利用div+css画线

上样式生成函数代码
lineStyle (x1, y1, x2, y2, lineWidth = 4, color = 'black') {

    let rectX = x1 < x2 ? x1 : x2;

    let rectY = y1 < y2 ? y1 : y2;

    let rectWidth = Math.abs(x1 - x2);

    let rectHeight = Math.abs(y1 - y2);

    //弦长

    let stringWidth = Math.ceil(Math.sqrt((rectWidth * rectWidth) + (rectHeight * rectHeight)));

    let xPad = (rectWidth - stringWidth) / 2;

    let yPad = (rectHeight - lineWidth) / 2;

    let radNum = Math.atan2((y1 - y2), (x1 - x2));

    return `

        position: absolute;

        width: ${ stringWidth }px;

        height: ${ lineWidth }px;

        background-color: ${ color };

        transform: translate(${ rectX + xPad }px, ${ rectY + yPad }px) rotate(${ radNum }rad);

    `;

},