如何使用java将PNG文件转换为PDF？

Posted 2023-03-28

【中文标题】如何使用java将PNG文件转换为PDF？

【英文标题】：How can I convert a PNG file to PDF using java?

【发布时间】：2012-01-11 19:28:23

【问题描述】：

有没有我可以使用的开源库？

【参考方案1】：

itext 可以帮助你。 您并没有真正将 png 转换为 pdf，而是创建一个包含 png 的 pdf。 简单的例子：

Document document = new Document(PageSize.A4, 20, 20, 20, 20);
PdfWriter.getInstance(document, new FileOutputStream("C:/test.pdf"));
document.open();
Image image = Image.getInstance(getClass().getResource("/logo.png"));
document.add(image);
document.close();

【参考方案2】：

如果横向模式更适合，则旋转页面的示例

/**
 * Converts arbitrary image file to PDF
 * http://***.com/a/42937466/241986
 * @param imageFile contents of JPEG or PNG file
 * @param outputStream stream to write out pdf, always closed after this method execution.
 * @throws IOException when there' an actual exception or image is not valid
 */
public static void imageToPdf(byte[] imageFile, OutputStream outputStream) throws IOException 
    try 
        Image image;
        try 
            image = Image.getInstance(imageFile);
         catch (BadElementException bee) 
            throw new IOException(bee);
        

        //See http://***.com/questions/1373035/how-do-i-scale-one-rectangle-to-the-maximum-size-possible-within-another-rectang
        Rectangle A4 = PageSize.A4;

        float scalePortrait = Math.min(A4.getWidth() / image.getWidth(),
                A4.getHeight() / image.getHeight());

        float scaleLandscape = Math.min(A4.getHeight() / image.getWidth(),
                A4.getWidth() / image.getHeight());

        // We try to occupy as much space as possible
        // Sportrait = (w*scalePortrait) * (h*scalePortrait)
        // Slandscape = (w*scaleLandscape) * (h*scaleLandscape)

        // therefore the bigger area is where we have bigger scale
        boolean isLandscape = scaleLandscape > scalePortrait;

        float w;
        float h;
        if (isLandscape) 
            A4 = A4.rotate();
            w = image.getWidth() * scaleLandscape;
            h = image.getHeight() * scaleLandscape;
         else 
            w = image.getWidth() * scalePortrait;
            h = image.getHeight() * scalePortrait;
        

        Document document = new Document(A4, 10, 10, 10, 10);

        try 
            PdfWriter.getInstance(document, outputStream);
         catch (DocumentException e) 
            throw new IOException(e);
        
        document.open();
        try 
            image.scaleAbsolute(w, h);
            float posH = (A4.getHeight() - h) / 2;
            float posW = (A4.getWidth() - w) / 2;

            image.setAbsolutePosition(posW, posH);
            image.setBorder(Image.NO_BORDER);
            image.setBorderWidth(0);

            try 
                document.newPage();
                document.add(image);
             catch (DocumentException de) 
                throw new IOException(de);
            
         finally 
            document.close();
        
     finally 
        outputStream.close();
    

在 pom.xml 中，免费的 iText 分支之一，如果你还没有使用 iText

<dependency>
    <groupId>com.github.librepdf</groupId>
    <artifactId>openpdf</artifactId>
    <version>1.0.1</version>
</dependency>

【讨论】：

使用这种方法如何在同一个文档上写入多个图像

我相信我最终将生成的 PDF 合并到另一个服务中。

这不是很难吗？你介意分享代码吗

【参考方案3】：

使用 iText 将 jpg/png/gif 转换为 pdf，代码如下。它的工作完美。

import java.io.FileOutputStream;
//com.lowagie...   old version
//com.itextpdf...  recent version
import com.itextpdf.text.Document;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.text.Image;

public class ImageToPDF 
  public static void main(String ... args) 
    Document document = new Document();
    String input = "c:/temp/capture.png"; // .gif and .jpg are ok too!
    String output = "c:/temp/capture.pdf";
    try 
      FileOutputStream fos = new FileOutputStream(output);
      PdfWriter writer = PdfWriter.getInstance(document, fos);
      writer.open();
      document.open();
      document.add(Image.getInstance(input));
      document.close();
      writer.close();
    
    catch (Exception e) 
      e.printStackTrace();
    
  

【参考方案4】：

用于读取 javax.imageio.ImageIO 用于编写pdf itext：http://itextpdf.com