<script language=javascript>

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>=500/400){

if(image.width>500){

imgd.width=500;

imgd.height=(image.height*500)/image.width;

}else{

imgd.width=image.width;

imgd.height=image.height;

}

}

else{

if(image.height>400){

imgd.height=400;

imgd.width=(image.width*400)/image.height;

}else{

imgd.width=image.width;

imgd.height=image.height;

}

}

}

}

</script>

调用方式（img是显示图片的html代 ） <img src= temp.jpg border=0 onload=javascript：drawimage(this);>

修改后：

<script language=javascript>

var flag=false; //控制小图

function drawimage(imgd,maxwidth,maxheight){

var image=new image();

image.src=imgd.src;

if(image.width>0 && image.height>0){

flag=true;

if(image.width/image.height>=maxwidth/maxheight){

if(image.width>maxwidth){

imgd.width=maxwidth;

imgd.height=(image.height*maxwidth)/image.width;

}else{

imgd.width=image.width;

imgd.height=image.height;

}

}

else{

if(image.height>maxheight){

imgd.height=maxheight;

imgd.width=(image.width*maxheight)/image.height;

}else{

imgd.width=image.width;

imgd.height=image.height;

}

}

}

}

</script>

呵呵，多了两个参数，也就是你能够接受的最大宽度maxwidth与最大高度maxheight