private int coverage(int x) {
    if ((x >= aaleftfull) && (x <= aarightfull) &&
        // important since not all SUBYRES lines may have been covered
        (firstModY == 0) && (lastModY == SUBYRES1)) {
      return 255;
    }

    int pixelLeft = x*SUBXRES;  // huh?
    int pixelRight = pixelLeft + 8;

    int amt = 0;
    for (int i = firstModY; i <= lastModY; i++) {
      if ((aaleft[i] > pixelRight) || (aaright[i] < pixelLeft)) {
        continue;
      }
      // does this need a +1 ?
      amt += ((aaright[i] < pixelRight ? aaright[i] : pixelRight) -
              (aaleft[i] > pixelLeft ? aaleft[i] : pixelLeft));
    }
    amt <<= 2;
    return (amt == 256) ? 255 : amt;
  }