int outSize = 200;

field#0(2)[] F = tent ⊛ load("../../data/ddro-115.nrrd");

strand sample (int ui, int vi) {
   real uu = lerp(0.0, 1.0, -0.5, real(ui), real(outSize)-0.5);
   real vv = lerp(0.0, 1.0, -0.5, real(vi), real(outSize)-0.5);
   vec2 pos = [uu, vv];
   output real val = -1.0; 

   update {
      val = F(pos) if (inside(pos,F)) else -1.0;
      stabilize;
   }
}

initially [ sample(ui, vi) | vi in 0..(outSize-1), ui in 0..(outSize-1) ];

<script type="text/javascript">//<![CDATA[
		function toggle_ffErrors() {
			var errorsblock = document.getElementById("ffErrorsBlock");
			var errorsgroup = document.getElementById("ffErrors");
			if (errorsblock.style.display == "none") {
				errorsblock.style.display = "block";
				errorsgroup.style.right = "10px";
			} else {
				errorsblock.style.display = "none";
				errorsgroup.style.right = "300px";
			}
		}
//]]></script>
<div id="ffErrors">
<a href="javascript:toggle_ffErrors();">Click to toggle</a>
<div id="ffErrorsBlock">
	<div class="error">does not end with &lt;/html&gt; tag</div>
	<div class="error">does not end with &lt;/body&gt; tag</div>
	<div class="info">The output has ended thus: 
      stabilize;
   }
}

initially [ sample(ui, vi) | vi in 0..(outSize-1), ui in 0..(outSize-1) ];</div>
</div></div>
</body></html>