function saveDomImage (html2Canvas, dom, fileName) {  //使用之前要引入 html2Canvas.js

        if(mui.os.plus){

            if (typeof html2Canvas == null)

                throw Error("html2Canvas is not defined");

            if (dom == null)

                throw Error("saveDomImage param : dom is null");

            if (fileName == null || fileName == "")

                fileName = "untitled.png";

            var getPixelRatio = function(context) {

                var backingStore = context.backingStorePixelRatio ||

                    context.webkitBackingStorePixelRatio || ;

                return (window.devicePixelRatio || ) / backingStore;

            };

            var _canvas = document.createElement('canvas');

            var ctx = _canvas.getContext('2d');

            var ratio = getPixelRatio(ctx);

            ctx.scale(ratio,ratio);

            var w = dom.offsetWidth;

            var h = dom.offsetHeight;

            _canvas.width = w;

            _canvas.height = h;

            _canvas.style.width = w *　ratio + 'px';

            _canvas.style.height = h　*　ratio + "px";

            html2Canvas(dom, {

                allowTaint:true,

                logging: false,

                profile: true,

                useCROS: true,

                canvas : _canvas,

                onrendered: function (canvas) {

                    var dataUrl = canvas.toDataURL();

                    var b = new plus.nativeObj.Bitmap('bitblmap');

                    b.loadBase64Data(dataUrl, function () {

                        /*这里一定要是_doc目录*/

                        b.save("_doc/" + fileName, {overwrite: true}, function (object) {

                            //保存到相册

                            plus.gallery.save("_doc/" + fileName, function () {

                                mui.toast("图片已保存到相册");

                            }, function () {

                                mui.toast("图片保存失败");

                            });

                        }, function () {

                            mui.toast("图片保存失败");

                        });

                    }, function () {

                        mui.toast("图片保存失败");

                    });

                }

            });

        }

    }