cb.saveState();
PdfGState gs1 = new PdfGState();
gs1.setFillOpacity(0.5f);
cb.setGState(gs1);
pictureCircles(200 + 2 * gap, 500, cb);
cb.restoreState();
PdfTemplate tp = cb.createTemplate(200, 200);
cb.saveState();
pictureCircles(0, 0, tp);
PdfTransparencyGroup group = new PdfTransparencyGroup();