srecord noeq FindRegionOutline(BWImage_FastRegions regions, int iRegion) {

  gettable new PtBuffer outline;

  int x, y, dx, dy;

  int polarity;

  run {

    Pt p = regions.samplePixel(iRegion);

    x = p.x;

    y = p.y;

    // move up until we're at the edge of the region

    // probably we don't actually need to do this because of the way

    // the image was scanned, but we'll do it anyway

    while (y > 0 && regions.inRegion(iRegion, x, y-1))

      y--;

    // found our first outline pixel with background above

    outline.add(x, y);

    // remember first point

    firstX = x; firstY = y;

    // start searching to the right

    dx = 1; dy = 0;

    int safety = (regions.getWidth()+2)*(regions.getHeight()+2);

    do {

      if (!findNextDirection())

        break;

    } while (x != firstX && y != firstY && l(outline) < safety);

  }

  void findNextDirection {

    // try directions (left, forward, right, turn around)

    Pt dir = turnLeft(dx, dy);

    repeat 4 {

      if (inRegion(x+dir.x, y+dir.y)) {

        dx = dir.x; dy = dir.y;

        true;

      }

    }

    false;

  }

    // forward?

    Pt left = turnLeft(dx, dy);

    if (inRegion(x+left.x, y+left.y)) {

      dx = left.x;

      dy = left.y;

    }

  }

}