用CSS绘制梯形

.mask1
{
    height: 0;
    width: 100px;
    border-top: 100px solid red;
    border-right: 37px solid transparent;
}

.mask2
{
    width:100px;
    height:0;
    border-width:0 37px 100px 37px;
    border-style:none solid solid;
    border-color:transparent transparent red;
}

.mask3
{
width:100px;
height:0;
border-top: 100px solid red;
border-right: 37px solid transparent;
border-left:37px solid transparent;
}

.mask4
{
width:100px;
height:0;
border-top:100px solid red;
border-left:37px solid transparent;
}