//图片按比例缩放
var flag=false;

//参数(图片,允许的宽度,允许的高度)
function DrawImage(ImgD,iwidth,iheight)
{
    var image=new Image();
    image.src=ImgD.src;
    if(image.width>0 && image.height>0)
    {
        flag=true;
        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;
            }
        //ImgD.alt=image.width+"×"+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;
            }
        //ImgD.alt=image.width+"×"+image.height;
        }
    }
}