[JS]获取图片原始宽高

function getImageNatural(img,cb){
                if (img.naturalWidth) { // 现代浏览器
                    nWidth = img.naturalWidth
                    nHeight = img.naturalHeight
                    cb({w:nWidth,h:nHeight})
                } else { // IE6/7/8
                    var image = new Image();
                    image.src = img.attr('src');
                    if(image.complete){
                        cb({w:image.width,h:image.height})
                    }else{
                        image.onload = function(){
                            var w = image.width;
                            var h = image.height;
                            cb({w:w,h:h})
                        }                           
                    }
                }
            }