Opening A Window

I am using the following code to display an image in a seperate
window.

<form>
<input type=button
onClick='window.open("image1.jpg","","width=260,height=260,resizable=0,border=0")'
value=Shhow Picture'>
</form>

I want the window to be the exact size of the image so I set the width
and height of the window the same as the width & height of the image.

The code works, however there is a white border on the top and left
side of the image. If I add 20 to the width and height of the window
then there is a white border around the whole image.

Is there anyway to have the window the exact size of the image,
without this white border? I know there is probably a simple solution,
but I'm a beginner at JavaScript.