java - 在 Java-GAE 上将 PDF 页面转换为 JPG

Question

我正在寻找一个开源 java 库，它使我能够在服务器端将 PDF 的单页呈现为 JPG 或 PNG。

不幸的是，它不能使用任何其他java.awt.*类

• java.awt.datatransfer.DataFlavor
• java.awt.datatransfer.MimeType
• java.awt.datatransfer.Transferable

如果有任何办法，一个小代码片段会很棒。

Answer 1

我相信icepdf可能有你正在寻找的东西。

我曾经使用过这个开源项目，将上传的 pdf 文件转换为图像，以便在在线目录中使用。

import org.icepdf.core.exceptions.PDFException;
import org.icepdf.core.exceptions.PDFSecurityException;
import org.icepdf.core.pobjects.Document;
import org.icepdf.core.pobjects.Page;
import org.icepdf.core.util.GraphicsRenderingHints;


public byte[][] convert(byte[] pdf, String format) {

    Document document = new Document();
    try {
        document.setByteArray(pdf, 0, pdf.length, null);

    } catch (PDFException ex) {
        System.out.println("Error parsing PDF document " + ex);
    } catch (PDFSecurityException ex) {
        System.out.println("Error encryption not supported " + ex);
    } catch (FileNotFoundException ex) {
        System.out.println("Error file not found " + ex);
    } catch (IOException ex) {
        System.out.println("Error handling PDF document " + ex);
    }
    byte[][] imageArray = new byte[document.getNumberOfPages()][];
    // save page captures to bytearray.
    float scale = 1.75f;
    float rotation = 0f;

    // Paint each pages content to an image and write the image to file
    for (int i = 0; i < document.getNumberOfPages(); i++) {
        BufferedImage image = (BufferedImage)
                document.getPageImage(i,
                                      GraphicsRenderingHints.SCREEN,
                                      Page.BOUNDARY_CROPBOX, rotation, scale);
       try {
            //get the picture util object
            PictureUtilLocal pum = (PictureUtilLocal) Component
            .getInstance("pictureUtil");
            //load image into util
            pum.loadBuffered(image);

            //write image in desired format
            imageArray[i] = pum.imageToByteArray(format, 1f);

            System.out.println("\t capturing page " + i);

        } catch (IOException e) {
            e.printStackTrace();
        }
        image.flush();
    }
    // clean up resources
    document.dispose();
    return imageArray;
}

不过请注意，这个库在 open-jdk 上抛出 SegFault 时遇到了麻烦。在 Sun 上运行良好。不确定它会在 GAE 上做什么。我不记得有问题的版本是什么，所以请注意。

Answer 2

您可以为此目的使用 apache PDF box APi并使用以下代码将两个 pdf 逐页转换为 JPG。

public  void convertPDFToJPG(String src,String FolderPath){

           try{
               File folder1 = new File(FolderPath+"\\");
               comparePDF cmp=new comparePDF();
               cmp.rmdir(folder1);

           //load pdf file in the document object
           PDDocument doc=PDDocument.load(new FileInputStream(src));
           //Get all pages from document and store them in a list
           List<PDPage> pages=doc.getDocumentCatalog().getAllPages();
           //create iterator object so it is easy to access each page from the list
           Iterator<PDPage> i= pages.iterator();
           int count=1; //count variable used to separate each image file
           //Convert every page of the pdf document to a unique image file
           System.out.println("Please wait...");
           while(i.hasNext()){
            PDPage page=i.next(); 
            BufferedImage bi=page.convertToImage();
            ImageIO.write(bi, "jpg", new File(FolderPath+"\\Page"+count+".jpg"));
            count++;
            }
           System.out.println("Conversion complete");
           }catch(IOException ie){ie.printStackTrace();}
          }