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;
    }
  }
}