使用PDFBox把pdf转PNG，且设置背景透明（但小部分图片背景仍是白色）

public static void main(String[] args) throws IOException {
    String src = "D:/test.pdf";
    String dest = "D:/test";
    PDDocument doc = null;
    try {
        doc = PDDocument.load(new File(src));
        PDFRenderer render = new PDFRenderer(doc);
        int count = doc.getNumberOfPages();
        for (int i = 0; i < count; i++) {
            // 设置背景透明
            BufferedImage image = render.renderImageWithDPI(i, 296, ImageType.ARGB);
            ImageIO.write(image, "PNG", new File(dest + File.separator + i + ".png"));
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (doc != null) {
            doc.close();
        }
    }
}

把图片放在pdf，再通过PDFBox转换成png，设置的背景色是不生效的