pictureBackdrop(200 + 2 * gap, 500, cb);
pictureBackdrop(gap, 500 - 200 - gap, cb);
pictureBackdrop(200 + 2 * gap, 500 - 200 - gap, cb);
pictureCircles(gap, 500, cb);
cb.saveState();
PdfGState gs1 = new PdfGState();
gs1.setFillOpacity(0.5f);
cb.setGState(gs1);
pictureCircles(200 + 2 * gap, 500, cb);
cb.restoreState();