修改上传文件按钮

HTML：

<form id="imgFile" action="" method="post" enctype="multipart/form-data">
                    <a href="javascript:void(0);" class="file">
                        上传头像
                        <input type="file" name="rp_pic_file" class="rp_pic_btn" id="upload_pic">
                    </a>
</form>

CSS：

.file {
    position: relative;
    display: inline-block;
    padding: 0;
    overflow: hidden;
    text-decoration: none;
    text-indent: 0;
    width:158px;
    height:50px;
    line-height:50px;
    -webkit-border-radius:20px;
    -moz-border-radius:20px;
    border-radius:20px;
    text-align: center;
    border: none;
    color: #000000;
    font-size:16px;
    background: #ffe400;
}
.file input {
    position: absolute;
    font-size: 100px;
    right: 0;
    top: 0;
    opacity: 0;
    filter: alpha(opacity=0);
}