java - 如何用java实现像pdf这样的网页浏览器渲染？

Question

我目前正在尝试制作一个 pdf 编写器应用程序，最终用户可以在 pdf 文件上绘制(线条/形状或文本)。我正在使用 pdfbox 将 pdf 文件显示到 jPanel 等 java swing 组件。 pdfbox 的问题是它渲染 pdf 文件的速度很慢，因为它使用 bufferedImage 然后绘制到 jPanel。该文件的分辨率也很差，我无法放大/缩小该文件。

我想实现一个类似于显示我的 pdf 文件的网络浏览器。

谢谢。

使用 pdfbox 将 pdf 转换为 bufferedImage 的代码。

import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.ImageType;
import org.apache.pdfbox.rendering.PDFRenderer;

public class Parse {

    private static File file;
    private int imageWidth;
    private int imageHeight;

    public Parse(File file) {
       this.file = file;
    }

    public BufferedImage getPage(int pageIndex) throws IOException {

       PDDocument pdf = PDDocument.load(file);  

       Float realWidth = new Float(pdf.getPage(0).getMediaBox().getWidth());
       Float realHeight = new 
       Float(pdf.getPage(0).getMediaBox().getHeight());

       Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
       Double ratio = .8;

       imageHeight = (int) (screenSize.getHeight() * ratio);
       imageWidth = (int) ((imageHeight * realWidth) / realHeight);

       PDFRenderer renderer = new PDFRenderer(pdf);

       BufferedImage renderImage = renderer.renderImage(pageIndex, 1, ImageType.RGB);
       pdf.close();
       return renderImage;
    }

    public int getImageWidth() {
       return imageWidth;
    }

    public void setImageWidth(int imageWidth) {
       this.imageWidth = imageWidth;
    }

    public int getImageHeight() {
       return imageHeight;
    }

    public void setImageHeight(int imageHeight) {
     this.imageHeight = imageHeight;
    }

}

将图像绘制到 JPanel 的代码。

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;

import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

public class PDFPanel extends JPanel {

    private Image image;
    private int width;
    private int height;

    public PDFPanel(Image image, int width, int height) {
        this.image = image;
        this.width = width;
        this.height = height;

        setBorder(new EmptyBorder(0, 0, 0, 0));
        setSize(width, height);
    }

    @Override
    protected void paintComponent(Graphics graphics) {
        super.paintComponent(graphics);
        Graphics2D graphics2D = (Graphics2D) graphics;
        graphics2D.drawImage(image, 0, 0, width, height, null);
    }

}

Answer 1

下面是一些使用 PDFBox 2.0 在 JPanel 中显示 PDF 的代码，基于问题 PDFBOX-3359 中提交的代码。它不能缩放，但可以改变大小。它仍然会很慢，而且窗口越大，速度就越慢。

public class PDFBox3359PanelTestEnhanced
{

    private static JPanel getTestPanel()
    {
        final PDDocument doc;
        try
        {
            doc = PDDocument.load(new File("XXXXX.pdf"));   

        }
        catch (IOException e)
        {
            e.printStackTrace();
            return null;
        }
        final PDFRenderer renderer = new PDFRenderer(doc);
        JPanel panel = new JPanel()
        {
            int i;

            @Override
            protected void paintComponent(Graphics g)
            {
                try
                {
                    g.setColor(Color.red);
                    g.fillRect(0, 0, getWidth(), getHeight());
                    PDPage page = doc.getPage(0);
                    PDRectangle cropBox = page.getCropBox();
                    boolean rot = false;
                    if (page.getRotation() == 90 || page.getRotation() == 270)
                    {
                        rot = true;
                    }

                    // https://stackoverflow.com/questions/1106339/resize-image-to-fit-in-bounding-box
                    float imgWidth = rot ? cropBox.getHeight() : cropBox.getWidth();
                    float imgHeight = rot ? cropBox.getWidth() : cropBox.getHeight();
                    float xf = getWidth() / imgWidth;
                    float yf = getHeight() / imgHeight;
                    float scale = Math.min(xf, yf);
                    if (yf < xf)
                    {
                        g.translate((int) ((getWidth() - imgWidth * yf) / 2), 0);
                    }
                    else
                    {
                        g.translate(0, (int) ((getHeight() - imgHeight * xf) / 2));
                    }
                    renderer.renderPageToGraphics(0, (Graphics2D) g, scale);
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
        };
        return panel;
    }

    public static void main(String[] args) throws Exception
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
                frame.add(getTestPanel());
                frame.pack();
                frame.setSize(600, 400);
                Dimension paneSize = frame.getSize();
                Dimension screenSize = frame.getToolkit().getScreenSize();
                frame.setLocation((screenSize.width - paneSize.width) / 2, (screenSize.height - paneSize.height) / 2);
                frame.setTitle("Test");
                frame.setVisible(true);
            }
        });
    }
}