Question

我一直在尝试将PDF转换为png文件，但透明度却没有成功。我尝试用很多方法解决它，但我没有成功。我正在写自己的方式，希望有人能找到错误的地方：

1

try (final PDDocument document = PDDocument.load(new File(srcpath))){
                PDFRenderer pdfRenderer = new PDFRenderer(document);
                for (int page = 0; page < document.getNumberOfPages(); ++page)
                {
                    BufferedImage bim = pdfRenderer.renderImageWithDPI(page, 300, ImageType.RGB);
                    String fileName = imageConverted;

                    boolean hasAlpha = bim.getColorModel().hasAlpha();
                System.out.println(hasAlpha);

                    ImageIOUtil.writeImage(bim, fileName, 300);
                }
                document.close();
            } catch (IOException e){
                System.err.println("Exception while trying to create pdf document - " + e);
            }

RandomAccessFile raf; 尝试{ raf = new RandomAccessFile（file，＆＃34; r＆＃34;）;

        FileChannel channel = raf.getChannel();
        ByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
        PDFFile pdffile = new PDFFile(buf);
        // draw the first page to an image
        int num=pdffile.getNumPages();
        for(int i=0;i<num;i++)
        {
            PDFPage page = pdffile.getPage(i);

            //get the width and height for the doc at the default zoom              
            int width=(int)page.getBBox().getWidth();
            int height=(int)page.getBBox().getHeight();             

            Rectangle rect = new Rectangle(0,0,width,height);
            int rotation=page.getRotation();
            Rectangle rect1=rect;
            if(rotation==90 || rotation==270)
                rect1=new Rectangle(0,0,rect.height,rect.width);

            //generate the image
            BufferedImage img = (BufferedImage)page.getImage(
                        rect.width, rect.height, //width & height
                        rect1, // clip rect
                        null, // null for the ImageObserver
                        true, // fill background with white
                        true  // block until drawing is done
                );
             Graphics2D graphics = (Graphics2D)img.getGraphics();
             graphics.setBackground( new Color( 255, 255, 255, 0 ) );

            ImageIO.write(img, "png", new File(imageConverted));
        }
    } 
    catch (FileNotFoundException e1) {
        System.err.println(e1.getLocalizedMessage());
    } catch (IOException e) {
        System.err.println(e.getLocalizedMessage());
    }

3

// Instantiating the PDFRenderer class
        PDFRenderer renderer = new PDFRenderer(document);

        // Rendering an image from the PDF document
        BufferedImage image = null;
        try {
             image= renderer.renderImage(0);
        } catch (IOException e1) {
            return "N/A";
        }

        // Writing the image to a file
        try {
            ImageIO.write(image, "png", new File(imageConverted));
        } catch (IOException e) {
            return "N/A";
        }

但是我得到了白色背景的png ...... 任何的想法？在此先感谢!!!

Answer 1

更改此行

BufferedImage bim = pdfRenderer.renderImageWithDPI(page, 300, ImageType.RGB);

到

BufferedImage bim = pdfRenderer.renderImageWithDPI(page, 300, ImageType.RGBA);

这将为您提供透明的图像。

将PDF转换为具有透明度的png文件（保持alpha）

1 个答案: