Java使用icepdf转高清图片

<dependency>
<groupId>org.icepdf.os</groupId>
<artifactId>icepdf-core</artifactId>
<version>6.1.2</version>
<exclusions>
<exclusion>
<groupId>javax.media</groupId>
<artifactId>jai-core</artifactId>
</exclusion>
</exclusions>
</dependency>

public static void pdf2Pic(String pdfPath, String path) throws IOException, PDFException, PDFSecurityException {
        org.icepdf.core.pobjects.Document document = new org.icepdf.core.pobjects.Document();
        document.setFile(pdfPath);
        //缩放比例
        float scale = 2.5f;
        //旋转角度
        float rotation = 0f;

        for (int i = 0; i < document.getNumberOfPages(); i++) {
            BufferedImage image = (BufferedImage)
                    document.getPageImage(i, GraphicsRenderingHints.SCREEN, org.icepdf.core.pobjects.Page.BOUNDARY_CROPBOX, rotation, scale);
            RenderedImage rendImage = image;
            try {
                String imgName = i + ".png";
                System.out.println(imgName);
                File file = new File(path + imgName);
                ImageIO.write(rendImage, "png", file);
            } catch (IOException e) {
                e.printStackTrace();
            }
            image.flush();
        }
        document.dispose();
    }

 String rootFolder = new File("").getAbsolutePath();

 pdf2Pic(rootFolder+"/pdf/4.pdf", rootFolder+"/pdf/n");