pdfbox將pdf轉換爲圖像byte []

Question

使用pdfbox，是否可以將PDF（或PDF字節[]）轉換爲圖像字節[]？我已經瀏覽了幾個在線的例子，我能找到的唯一例子描述瞭如何直接將轉換後的文件寫入文件系統或將其轉換爲Java AWT對象。

我寧願不招致將圖像文件寫入文件系統的IO，讀入一個字節[]，然後將其刪除。

所以這個我可以這樣做：

String destinationImageFormat = "jpg"; 
boolean success = false; 
InputStream is = getClass().getClassLoader().getResourceAsStream("example.pdf"); 
PDDocument pdf = PDDocument.load(is, true); 

int resolution = 256; 
String password = ""; 
String outputPrefix = "myImageFile"; 

PDFImageWriter imageWriter = new PDFImageWriter();  

success = imageWriter.writeImage(pdf, 
        destinationImageFormat, 
        password, 
        1, 
        2, 
        outputPrefix, 
        BufferedImage.TYPE_INT_RGB, 
        resolution); 

除了這一點：

InputStream is = getClass().getClassLoader().getResourceAsStream("example.pdf"); 

PDDocument pdf = PDDocument.load(is, true); 
List<PDPage> pages = pdf.getDocumentCatalog().getAllPages(); 

for (PDPage page : pages) 
{ 
    BufferedImage image = page.convertToImage(); 
} 

如果我不是清楚是怎麼變換分析數據的BufferedImage成一個byte []。我知道這是轉換成imageWriter.writeImage（）中的文件輸出流，但我不清楚API的工作原理。

Answer 1

您可以使用ImageIO.write寫入OutputStream。要得到一個字節[]，請使用ByteArrayOutputStream，然後在其上調用toByteArray（）。

Answer 2

try {   
       PDDocument document = PDDocument.load(PdfInfo.getPDFWAY()); 
       if (document.isEncrypted()) { 
        document.decrypt(PdfInfo.getPASSWORD()); 
       } 
       if ("bilevel".equalsIgnoreCase(PdfInfo.getCOLOR())) { 
        PdfInfo.setIMAGETYPE(BufferedImage.TYPE_BYTE_BINARY); 
       } else if ("indexed".equalsIgnoreCase(PdfInfo.getCOLOR())) { 
        PdfInfo.setIMAGETYPE(BufferedImage.TYPE_BYTE_INDEXED); 
       } else if ("gray".equalsIgnoreCase(PdfInfo.getCOLOR())) { 
        PdfInfo.setIMAGETYPE(BufferedImage.TYPE_BYTE_GRAY); 
       } else if ("rgb".equalsIgnoreCase(PdfInfo.getCOLOR())) { 
        PdfInfo.setIMAGETYPE(BufferedImage.TYPE_INT_RGB); 
       } else if ("rgba".equalsIgnoreCase(PdfInfo.getCOLOR())) { 
        PdfInfo.setIMAGETYPE(BufferedImage.TYPE_INT_ARGB); 
       } else { 
        System.exit(2); 
       } 
       PDFImageWriter imageWriter = new PDFImageWriter(); 
       boolean success = imageWriter.writeImage(document, PdfInfo.getIMAGE_FORMAT(),PdfInfo.getPASSWORD(), 
         PdfInfo.getSTART_PAGE(),PdfInfo.getEND_PAGE(),PdfInfo.getOUTPUT_PREFIX(),PdfInfo.getIMAGETYPE(),PdfInfo.getRESOLUTION()); 
       if (!success) { 
        System.exit(1); 
       } 
       document.close(); 

     } catch (IOException | CryptographyException | InvalidPasswordException ex) { 
      Logger.getLogger(PdfToImae.class.getName()).log(Level.SEVERE, null, ex); 
     } 
public class PdfInfo { 
    private static String PDFWAY;  
    private static String OUTPUT_PREFIX; 
    private static String PASSWORD; 
    private static int START_PAGE=1; 
    private static int END_PAGE=Integer.MAX_VALUE; 
    private static String IMAGE_FORMAT="jpg"; 
    private static String COLOR="rgb"; 
    private static int RESOLUTION=256; 
    private static int IMAGETYPE=24; 
    private static String filename; 
    private static String filePath=""; 
} 

Answer 3

添加Maven的依賴：

<!-- https://mvnrepository.com/artifact/org.apache.pdfbox/pdfbox --> 
    <dependency> 
     <groupId>org.apache.pdfbox</groupId> 
     <artifactId>pdfbox</artifactId> 
     <version>2.0.1</version> 
    </dependency> 

而且，CONVER一個PDF格式的圖像：

import org.apache.pdfbox.pdmodel.PDDocument; 
import org.apache.pdfbox.rendering.PDFRenderer; 
import javax.imageio.ImageIO; 

private List<String> savePDF(String filePath) throws IOException { 
    List<String> result = Lists.newArrayList(); 

    File file = new File(filePath); 

    PDDocument doc = PDDocument.load(file); 
    PDFRenderer renderer = new PDFRenderer(doc); 

    int pageSize = doc.getNumberOfPages(); 
    for (int i = 0; i < pageSize; i++) { 
     String pngFileName = file.getPath() + "." + (i + 1) + ".png"; 

     FileOutputStream out = new FileOutputStream(pngFileName); 
     ImageIO.write(renderer.renderImageWithDPI(i, 96), "png", out); 
     out.close(); 

     result.add(pngFileName); 
    } 
    doc.close(); 
    return result; 
} 

編輯：

import org.apache.pdfbox.pdmodel.PDDocument; 
import org.apache.pdfbox.rendering.PDFRenderer; 
import javax.imageio.ImageIO; 

private List<String> savePDF(String filePath) throws IOException { 
    List<String> result = Lists.newArrayList(); 

    File file = new File(filePath); 

    PDDocument doc = PDDocument.load(file); 
    PDFRenderer renderer = new PDFRenderer(doc); 

    int pageSize = doc.getNumberOfPages(); 
    for (int i = 0; i < pageSize; i++) { 
     String pngFileName = file.getPath() + "." + (i + 1) + ".png"; 

     ByteArrayOutputStream out = new ByteArrayOutputStream(pngFileName); 
     ImageIO.write(renderer.renderImageWithDPI(i, 96), "png", out); 

     out.toByteArray(); // here you can get a byte array 

     out.close(); 

     result.add(pngFileName); 
    } 
    doc.close(); 
    return result; 
}