图片按比例缩放

<script language="JavaScript"><!--//图片按比例缩放var flag=false;function DrawImage(ImgD,iwidth,iheight){    //参数(图片,允许的宽度,允许的高度)    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;        }    }}//--></script>