css图片根据div宽高比例自适应

1.div布局

<div class="card-img-show">
                            <div class="upload-img-conss" >
                                <img style=" 200px" class="addPersonFile"  id="personImg" :src="personImgDataUrl" >
                                <div class="upload-img-success-bg">
                                    <div class="upload-promise-img-chuan-margin">
                                    </div>
                                    <p class="upload-img-add-front" style="margin-top: 11px; padding-left: 0">证件有效信息面</p>
                                </div>
                            </div>
                        <div class="card-img-show">
                        <input style="position: absolute;  52%; height: 73%" class="register-person-260-upload" :class="{'is-danger': errors.has('cardImg') }" v-validate="'required|unitCardImg'" name="cardImg" type="file"  id="addPersonFile" v-on:change="getFile($event)"
                               placeholder="请上传证件照">
                            <p v-show="errors.has('cardImg')" style="display:none;color: red;font-size: 12px;">{{ errors.first('cardImg') }}</p>
                     
                        <p class="card-img-show-p">文件格式为：jpg或png；文件大小：1M至5M</p>
                        </div>
                    </div>

　　效果图

根据图片原始尺寸等比缩放，不拉伸图片宽高；

前端使用vue框架：图片上传完成后渲染

updated(){
            $(".register-container img").each(function(){
                if(!!$(this).attr("src") && $(this).attr("src").indexOf("http")>-1){
                    var imgid= $(this).attr("id")
                     //添加遮罩可忽略
                    $("#"+imgid+"+ div:first").addClass("upload-img-success-bg-change");
                    //图片id
                    var img = $(this);
                    //图片自适应宽高
                    imgSuite(imgid,img);
                }
            });
        },

　公共js方法

function imgSuite(imgid,img) {
	var realWidth;//真实的宽度
	var realHeight;//真实的高度
    //虚拟img标签
	$("<img/>").attr("src", $(img).attr("src")).on('load',function() {
		realWidth = this.width;
		realHeight = this.height;
		var upPercent = realWidth/realHeight;
		var parentDiv = $("#"+imgid).parent();
		var parentWidth =  parentDiv.width();//父级宽
		var parentHeight =  parentDiv.height();//父级高
		var orgPercent = parentWidth/parentHeight;
		if(upPercent<orgPercent){
			$("#"+imgid).css({"auto",height:parentHeight+"px",margin:"0 auto",display:"block"});
		}else {
			var differHeight = parentWidth*realHeight/realWidth;//父级高度减去图片高度差
			var marginTop = (parentHeight - differHeight)/2;//距离顶部高
			$("#"+imgid).css({height:"auto",parentWidth+"px",marginTop: marginTop + "px",display:"block"});
		}
	});
}