使用itext7将图像作为透明水印添加到pdf

Question

我想使用itext7作为透明水印将图像添加到pdf中。我正在使用pdfcanvas和PdfExtGState。但图片显示在页面文字的顶部。虽然文本没有丢失，但是变得越来越模糊。我想解决这个问题。预期的结果是将图像推到背景，并且文本应显示在其顶部。

PdfDocument bodyPDFDoc = new PdfDocument(new PdfReader(in_filePath+pdfDest.getName()), new PdfWriter(in_filePath+fileName1+"_WATERMARK.pdf"));
                Document bodyDoc = new Document(bodyPDFDoc);
                int numPages = bodyPDFDoc.getNumberOfPages();
                ImageData img = ImageDataFactory.create(in_watermarkImgFileName);// NEED TO GIVE WATERMARK FILE PATH
                float w = img.getWidth();
                float h = img.getHeight();

                // transparency
                PdfExtGState gs1 = new PdfExtGState();
                gs1.setFillOpacity(0.2f);

                // properties
                PdfCanvas canvasBodyPDFDoc = null;
                Rectangle pagesize;
                float x, y;
                // loop over every page
                for (int pageNo = 1; pageNo <= numPages; pageNo++) {
                    if(pageNo>1){
                        pagesize = bodyPDFDoc.getPage(pageNo).getPageSize();
                        x = (pagesize.getLeft() + pagesize.getRight()) / 2;
                        y = (pagesize.getTop() + pagesize.getBottom()) / 2;
                        canvasBodyPDFDoc = new PdfCanvas(bodyPDFDoc.getPage(pageNo));
                        canvasBodyPDFDoc.saveState();
                        canvasBodyPDFDoc.setExtGState(gs1);
                        canvasBodyPDFDoc.addImage(img, w, 0, 0, h, x - (w / 2), y - (h / 2), false);
                        canvasBodyPDFDoc.restoreState();
                    }
}

请帮助。