var flag=false; 
function DrawImage(ImgD){ 
var image=new Image(); 
image.src=ImgD.src; 
if(image.width>0 && image.height>0){ 
flag=true; 
if(image.width/image.height>= 500/600){ 
if(image.width>500){ 
ImgD.width=500; 
ImgD.height=(image.height*500)/image.width; 
}else{ 
ImgD.width=image.width; 
ImgD.height=image.height; 
} 
ImgD.alt=image.width+"x"+image.height; 
} 
else{ 
if(image.height>600){ 
ImgD.height=600; 
ImgD.width=(image.width*600)/image.height; 
}else{ 
ImgD.width=image.width; 
ImgD.height=image.height; 
} 
ImgD.alt=image.width+"x"+image.height; 
} 
} 
} 




<!-- 
//图片按比例缩放 

function   DrawImage1(ImgD){ 
var   image=new   Image(); 
var   iwidth   =   205;   //定义允许图片宽度 
var   iheight   =   160;   //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) "> 
//--> 


<!-- 
//图片按比例缩放 

function   DrawImage2(ImgD){ 
var   image=new   Image(); 
var   iwidth   =   135;   //定义允许图片宽度 
var   iheight   =   130;   //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) "> 
//-->