//图片按比例缩放

var flag=false;
function DrawImage(ImgD,width,height)
{
    var image=new Image();
    var iwidth = width; //定义允许图片宽度
    var iheight = height; //定义允许图片高度
    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;
        } 
    }
}
//调用：<img src="图片" onload="javascript:DrawImage(this,width,height)">