//图片按比例缩放,可输入参数设定初始大小
        function resizeimg(ImgD,iwidth,iheight)
        {
            var image=new Image();
            image.src=ImgD.src;
            if(image.width>0 && image.height>0)
            {
                if(image.width/image.height>= iwidth/iheight)
                {
                    if(image.width>iwidth)
                    {
                        ImgD.width=iwidth;
                        ImgD.height=(image.height*iwidth)/image.width;
                    }
                    else
                    {
                        ImgD.width=image.width;
                        ImgD.height=image.height;
                    }
                }
                else
                {
                    if(image.height>iheight)
                    {
                        ImgD.height=iheight;
                        ImgD.width=(image.width*iheight)/image.height;
                    }
                    else
                    {
                        ImgD.width=image.width;
                        ImgD.height=image.height;
                    }
                }
            }
        }