public void ensureBlack() {
		for (int i = 0; i < ximlen; i++) {
			for (int j = 0; j < yimlen; j++) {
				if (img_alpha[i][j] > 0) {
					img_red[i][j] -= (long) ((double) img_red[i][j] / img_alpha[i][j]);
					img_green[i][j] -= (long) ((double) img_green[i][j] / img_alpha[i][j]);
					img_blue[i][j] -= (long) ((double) img_blue[i][j] / img_alpha[i][j]);
				}

				if (runtotal % 100 == 40) {
					img_red[i][j] /= 2;
					img_green[i][j] /= 2;
					img_blue[i][j] /= 2;
					img_alpha[i][j] /= 2;
				}
			}
		}
		limit += 2;
		quad -= 2;
	}