<!-- le clip-path -->
<clipPath id="leClip" clipPathUnits="objectBoundingBox">  
  <path d="M 0 0.5
           a 0.5 0.5 0 0 0  0.5 -0.5
           a 0.5 0.5 0 0 0  0.5  0.5
           a 0.5 0.5 0 0 0 -0.5  0.5
           a 0.5 0.5 0 0 0 -0.5 -0.5"/>
</clipPath>

					
<!-- l'image 'clipé' -->
<image xlink:href="expocouleur.jpg"
       x="0" y="0" width="128" height="128"
       clip-path="url(#leClip)" />