问无法仅在skia生成的pdf上使用itext7和Java语言放置图章(显示反转图章)

EN

public void createPdf(String src, String dest) throws IOException {
    PdfDocument pdfDoc = new PdfDocument(
            new PdfReader(src), new PdfWriter(dest));
    Document document = new Document(pdfDoc);
    PdfCanvas over;
    PdfExtGState gs1 = new PdfExtGState();
    gs1.setFillOpacity(0.5f);
    int n = pdfDoc.getNumberOfPages();
    Rectangle pagesize;
    ImageData img = ImageDataFactory.create(IMG);
    float iW = img.getWidth();
    float iH = img.getHeight();
    float x, y;

    for (int i = 1; i <= n; i++)
    {
        PdfPage pdfPage = pdfDoc.getPage(i);
        pagesize = pdfPage.getPageSize();

        x = pagesize.getLeft();
        y = pagesize.getTop() - iH;

        over = new PdfCanvas(pdfDoc.getPage(i));

        over.saveState();
        over.setExtGState(gs1);

        over.addImage(img, iW, 0, 0, iH, x, y);

        over.restoreState();
    }
    document.close();
    pdfDoc.close();
}