input type= file 如何更改自定义的样式

input {
@include wh(24px,22px);//sass 宽高
@include pa(0,0);      //绝对定位 top：0；left：0；
opacity: 0;            //透明度；
overflow: hidden;
}
让input type=file 文件改变宽高，透明绝对定位在 点击按钮或者图标的下边，就可以美化自定义上传的文件了；

<ul class="chat-dialog-tools-list clr" id="carousel">
<li @click.stop="toggleEm($event)">
<i class="icons em-icon" title="选择表情"></i>
</li>
<li>

<i class="icons pic-icon">
<!--<input type="file" id="selectFile" @change="sendFile()"  accept="image/jpeg, image/gif, image/x-ms-bmp, image/x-png">-->
<input type="file" id="selectImage" title="发送图片" accept="image/jpeg, image/gif, image/x-ms-bmp, image/x-png">
</i>
</li>
<li @click.stop="doCapture()">
<i class="icons cut-icon" title="屏幕截图"></i>
</li>

<li>
<i class="icons file-icon" title="发送文件">
<!--<input type="file" id="selectFile" >-->
</i>
</li>
<li>
<i class="icons mail-icon" title="发送邮件">

</i>
</li>
<li>
<i class="icons news-icon" title="历史消息"></i>
</li>
<li class="chat-dialog-video">
<i class="icons video-icon" title="视频通话"></i>
</li>
<li class="chat-dialog-voice">
<i class="icons voice-icon" title="音频通话"></i>
</li>

</ul>