web页面打印--铺满A4

css

    <style type="text/css">
         body {
             margin: 0;
             padding: 0;
             background-color: #FAFAFA;
             font: 12pt "Tahoma";
         }

         * {
             box-sizing: border-box;
             -moz-box-sizing: border-box;
         }

         .page {
             width: 21cm;
             min-height: 29.7cm;
             padding: 2cm;
             margin: 1cm auto;
             border: 1px #D3D3D3 solid;
             border-radius: 5px;
             background: white;
             box-shadow: 0 0 5px rgba(0, 0, 0, 0.1);
         }

         .subpage {
             padding: 1cm;
             border: 5px red solid;
             height: 297mm;
             overflow: visible;
             outline: 2cm #FFEAEA solid;
             background-color: dodgerblue;
         }

         @@page {
             size: A4;
             margin: 0;
         }

         @@media print {
             .page {
                 margin: 0;
                 border: initial;
                 border-radius: initial;
                 width: initial;
                 min-height: initial;
                 box-shadow: initial;
                 background: initial;
                 page-break-after: always;
             }
         }
     </style>

html

  <div id="divContent" style="width:800px;margin:0 auto;">
         <div id="printCtrl" style="width:300px;margin:0 auto;">
             <object classid="CLSID:8856F961-340A-11D0-A96B-00C04FD705A2" height="0" id="WebBrowser" width="0"></object>
             <a href="javascript:void(0)" class="easyui-linkbutton" onclick="printSet()" style="width:80px">打印设置</a>
             <a href="javascript:void(0)" class="easyui-linkbutton" onclick="printPreview()" style="width:80px">打印预览</a>
             <a href="javascript:void(0)" class="easyui-linkbutton" onclick="print()" style="width:80px">打印</a>
         </div>
         <div id="divContentUL">
             <div class="page">
                 <div class="subpage">
                     <img src="" onload="imgOnload(this)" />
                 </div>
             </div>
         </div>
     </div>

javascript

  function imgOnload(obj) {
             var _this = obj;
             var $parent = $(_this).parent();
             var parent_width = $parent.width();//容器宽度
             var parent_height = $parent.height();//容器高度
             var img_width_old = _this.width;//图片宽度
             var img_height_old = _this.height;//图片高度

             var vImgRWH = img_width_old / img_height_old;//图片宽高比例
             var vParentRWH = parent_width / parent_height;//容器宽高比例
             if (vImgRWH <= vParentRWH) {
                 var vW = parent_width / img_width_old;
                 var vH = parent_height / img_height_old;
                 var vv = vW >= vH ? vH : vW;
                 _this.width = img_width_old * vv;
                 _this.height = img_height_old * vv;
             }
             else {
                 var vH = parent_height / img_width_old;
                 var vW = parent_width / img_height_old;
                 if (vH > vW) {
                     _this.width = img_width_old * vW;
                     _this.height = img_height_old * vW;
                 }
                 else {
                     _this.width = img_width_old * vH;
                     _this.height = img_height_old * vH;
                 }
                 _this.style.transform = "rotate(90deg)";
                 _this.style.marginTop = (_this.width - _this.height) / 2 + "px";
                 _this.style.marginLeft = (_this.height - _this.width) / 2 + "px";

             }

         };

         function print() {
             var printCtrl = document.getElementById("printCtrl");
             printCtrl.style.display = "none";
             document.all.WebBrowser.ExecWB(6, 1);
             printCtrl.style.display = "";
         }

         function printPreview() {
             var printCtrl = document.getElementById("printCtrl");
             printCtrl.style.display = "none";
             document.all.WebBrowser.ExecWB(7, 1);
             printCtrl.style.display = "";
         }

         function printSet() {
             document.all.WebBrowser.ExecWB(8, 1);
         }