java - 使用pdfbox库java从PDF中提取图像

Question

我只想要 pdf 中各自位置的图像及其确切的布局，但我不想在其中呈现文本目前有什么方法可以做到这一点我正在以这种方式工作，但文本也出现在这个那么有没有办法满足这个要求

             File sourceFile=new File(pdfFile);
             String fileName = sourceFile.getName().replace(".pdf", "");             
             int pageNumber = 1;
             for (PDPage page : li) 
             {
                 BufferedImage image = page.convertToImage();
                 File outputfile = new File(imgDes + fileName +"_"+ pageNumber +".png");
                 System.out.println("Image Created -> "+ outputfile.getName());
                 ImageIO.write(image, "png", outputfile);
                 pageNumber++;
             }

Answer 1

从PageDrawer派生一个类，将所有不处理图像的方法用空覆盖，然后调用drawPage()。我只是覆盖了 processTextPosition()，并没有理会线条、形状等，但我认为我的意思很清楚。

public class MyPageDrawer extends PageDrawer
{

    public MyPageDrawer() throws IOException
    {
    }

    @Override
    protected void processTextPosition(TextPosition text)
    {
    }

    // taken from PDPage.convertToImage, with extra parameter and one modification
    static BufferedImage convertToImage(PDPage page, int imageType, int resolution) throws IOException
    {
        final Color TRANSPARENT_WHITE = new Color(255, 255, 255, 0);
        final int DEFAULT_USER_SPACE_UNIT_DPI = 72;

        PDRectangle cropBox = page.findCropBox();
        float widthPt = cropBox.getWidth();
        float heightPt = cropBox.getHeight();
        float scaling = resolution / (float) DEFAULT_USER_SPACE_UNIT_DPI;
        int widthPx = Math.round(widthPt * scaling);
        int heightPx = Math.round(heightPt * scaling);
        Dimension pageDimension = new Dimension((int) widthPt, (int) heightPt);
        int rotationAngle = page.findRotation();
        // normalize the rotation angle
        if (rotationAngle < 0)
        {
            rotationAngle += 360;
        }
        else if (rotationAngle >= 360)
        {
            rotationAngle -= 360;
        }
        // swap width and height
        BufferedImage retval;
        if (rotationAngle == 90 || rotationAngle == 270)
        {
            retval = new BufferedImage(heightPx, widthPx, imageType);
        }
        else
        {
            retval = new BufferedImage(widthPx, heightPx, imageType);
        }
        Graphics2D graphics = (Graphics2D) retval.getGraphics();
        graphics.setBackground(TRANSPARENT_WHITE);
        graphics.clearRect(0, 0, retval.getWidth(), retval.getHeight());
        if (rotationAngle != 0)
        {
            int translateX = 0;
            int translateY = 0;
            switch (rotationAngle)
            {
                case 90:
                    translateX = retval.getWidth();
                    break;
                case 270:
                    translateY = retval.getHeight();
                    break;
                case 180:
                    translateX = retval.getWidth();
                    translateY = retval.getHeight();
                    break;
                default:
                    break;
            }
            graphics.translate(translateX, translateY);
            graphics.rotate((float) Math.toRadians(rotationAngle));
        }
        graphics.scale(scaling, scaling);
        PageDrawer drawer = new MyPageDrawer(); // MyPageDrawer instead of PageDrawer
        drawer.drawPage(graphics, page, pageDimension);
        drawer.dispose();
        graphics.dispose();
        return retval;
    }

    public static void main(String[] args) throws IOException
    {
        String filename = "......./blah.pdf";

        // open the document
        PDDocument doc = PDDocument.loadNonSeq(new File(filename), null);
        List<PDPage> pages = doc.getDocumentCatalog().getAllPages();
        for (int p = 0; p < pages.size(); ++p)
        {
            PDPage page = pages.get(p);
            BufferedImage bim = convertToImage(page, BufferedImage.TYPE_INT_RGB, 300);

            boolean b = ImageIOUtil.writeImage(bim, "page-" + (p + 1) + ".png", 300);
            if (!b)
            {
                // error handling
            }
        }
        doc.close();
    }

}