off the top of my head... instead of a img tag, use a div tag, apply a background image, and then use a transparent gif with the width and height set to 100%
Like so:
HTML:
<div style="background-image:URL('image.jpg');height:height_of_image_px;width:width_of_image_px;">
<img src="transparent_gif.gif" height="100%" width="100%">
</div>