code: private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {
  
      int[] enclosingRectangle = image.getEnclosingRectangle();
      if (enclosingRectangle == null) {
        throw NotFoundException.getNotFoundInstance();
      }
  
      int left = enclosingRectangle[0];
      int top = enclosingRectangle[1];
      int width = enclosingRectangle[2];
      int height = enclosingRectangle[3];
  
      // Now just read off the bits
      BitMatrix bits = new BitMatrix(MATRIX_WIDTH, MATRIX_HEIGHT);
      for (int y = 0; y < MATRIX_HEIGHT; y++) {
        int iy = top + (y * height + height / 2) / MATRIX_HEIGHT;
        for (int x = 0; x < MATRIX_WIDTH; x++) {
          int ix = left + (x * width + width / 2 + (y & 0x01) *  width / 2) / MATRIX_WIDTH;
          if (image.get(ix, iy)) {
            bits.set(x, y);
          }
        }
      }
      return bits;
    }
docs: This method detects a code in a "pure" image -- that is, pure monochrome image
  which contains only an unrotated, unskewed, image of a code, with some white border
  around it. This is a specialized method that works exceptionally fast in this special
  case.