file按钮美化成图片（纯HTML+CSS）

                <div>
                    <h2>上传头像</h2>
                    <p class="fs18">(请上传200X200px大小的JPEG或PNG图片)</p>
                    <form>
                        <a class="btn_addPic mlr-auto" href="javascript:void(0);">
                            <img src="img/添加_关闭按钮.png"/>
                            <input class="filePrew" type="file" name="pic">
                        </a>
                    </form>
                </div>

            .btn_addPic{
                display: block; 
                position: relative; 
                width: 53px; 
                height: 53px; 
                overflow: hidden; 
                cursor: pointer; 
                text-align: center; 
            }
            .filePrew { 
                display: block; 
                position: absolute; 
                top: 0; 
                left: 0; 
                width: 53px; 
                height: 53px; 
                opacity: 0;
            }