Sorry for the noise: I think I answered my own question. You basically stick a pinhole in the image you want to place at its desired center, you put a pinhole on the scene at the place you want the image to go, and you use overlay/pinhole to place the image (or place-image/align, and use 'pinhole as the x-place and y-place.) I'm still a little confused by the use of place-image/align, since it seems like you need to utter the location that you're pinning the image to twice, once in the coordinates for place-image/align, and once in the pinhole you place on the scene. But it does seem to work. y <div class="gmail_quote">On Sat, Feb 5, 2011 at 10:05 PM, Yaron Minsky <<a href="mailto:yminsky@gmail.com">yminsky@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> In playing around with image.ss, I've run into the following problem: the center of an image does not appear to be rotation invariant. Thus, if you use place-image/align in order to place a triangle, say, that you then rotate continuously, you will see the triangle wobble as its effective center moves around. Is there any way around this? I tried using pinholes, but pinholes seem to require that all images involved have pinholes, which is not quite what I'm going for. What I really want to do is to declare a stable center for an image, but I can't quite figure out how to do that. y </blockquote></div>