我针对您发送给我的两个文件运行了ExtractImages.java。问题文件有 CMYK 图像，从 PDFDebugger 的截图可以看出：
问题是1.8版本不能正确处理CMYK图像。
但是有一个技巧：
图像使用 DCTDecode 过滤器进行编码，该过滤器是 JPEG。 PDF 中有“真正的 JPEG”。
我可以通过使用该工具的“-directJPEG”选项正确提取您的图像，该选项绕过 PDFBox 的解码机制，并“按原样”保存 JPEG 文件。
请注意，虽然这适用于您的文件，但如果图像具有在 PDF 中指定的外部色彩空间，它就无法正常工作。
这是完整的源代码。有关原始提取详细信息，请参见 writeJpeg2file()。
public class ExtractImages
{
private int imageCounter = 1;
private static final String PASSWORD = "-password";
private static final String PREFIX = "-prefix";
private static final String ADDKEY = "-addkey";
private static final String NONSEQ = "-nonSeq";
private static final String DIRECTJPEG = "-directJPEG";
private static final List<String> DCT_FILTERS = new ArrayList<String>();
static
{
DCT_FILTERS.add( COSName.DCT_DECODE.getName() );
DCT_FILTERS.add( COSName.DCT_DECODE_ABBREVIATION.getName() );
}
private ExtractImages()
{
}
/**
* This is the entry point for the application.
*
* @param args The command-line arguments.
*
* @throws Exception If there is an error decrypting the document.
*/
public static void main( String[] args ) throws Exception
{
ExtractImages extractor = new ExtractImages();
extractor.extractImages( args );
}
private void extractImages( String[] args ) throws Exception
{
if( args.length < 1 || args.length > 4 )
{
usage();
}
else
{
String pdfFile = null;
String password = "";
String prefix = null;
boolean addKey = false;
boolean useNonSeqParser = false;
boolean directJPEG = false;
for( int i=0; i<args.length; i++ )
{
if( args[i].equals( PASSWORD ) )
{
i++;
if( i >= args.length )
{
usage();
}
password = args[i];
}
else if( args[i].equals( PREFIX ) )
{
i++;
if( i >= args.length )
{
usage();
}
prefix = args[i];
}
else if( args[i].equals( ADDKEY ) )
{
addKey = true;
}
else if( args[i].equals( NONSEQ ) )
{
useNonSeqParser = true;
}
else if( args[i].equals( DIRECTJPEG ) )
{
directJPEG = true;
}
else
{
if( pdfFile == null )
{
pdfFile = args[i];
}
}
}
if(pdfFile == null)
{
usage();
}
else
{
if( prefix == null && pdfFile.length() >4 )
{
prefix = pdfFile.substring( 0, pdfFile.length() -4 );
}
PDDocument document = null;
try
{
if (useNonSeqParser)
{
document = PDDocument.loadNonSeq(new File(pdfFile), null, password);
}
else
{
document = PDDocument.load( pdfFile );
if( document.isEncrypted() )
{
StandardDecryptionMaterial spm = new StandardDecryptionMaterial(password);
document.openProtection(spm);
}
}
AccessPermission ap = document.getCurrentAccessPermission();
if( ! ap.canExtractContent() )
{
throw new IOException(
"Error: You do not have permission to extract images." );
}
List pages = document.getDocumentCatalog().getAllPages();
Iterator iter = pages.iterator();
while( iter.hasNext() )
{
PDPage page = (PDPage)iter.next();
PDResources resources = page.getResources();
// extract all XObjectImages which are part of the page resources
processResources(resources, prefix, addKey, directJPEG);
}
}
finally
{
if( document != null )
{
document.close();
}
}
}
}
}
public void writeJpeg2file(PDJpeg image, String filename) throws IOException
{
FileOutputStream out = null;
try
{
out = new FileOutputStream(filename + ".jpg");
InputStream data = image.getPDStream().getPartiallyFilteredStream(DCT_FILTERS);
byte[] buf = new byte[1024];
int amountRead;
while ((amountRead = data.read(buf)) != -1)
{
out.write(buf, 0, amountRead);
}
IOUtils.closeQuietly(data);
out.flush();
}
finally
{
if (out != null)
{
out.close();
}
}
}
private void processResources(PDResources resources, String prefix,
boolean addKey, boolean directJPEG) throws IOException
{
if (resources == null)
{
return;
}
Map<String, PDXObject> xobjects = resources.getXObjects();
if( xobjects != null )
{
Iterator<String> xobjectIter = xobjects.keySet().iterator();
while( xobjectIter.hasNext() )
{
String key = xobjectIter.next();
PDXObject xobject = xobjects.get( key );
// write the images
if (xobject instanceof PDXObjectImage)
{
PDXObjectImage image = (PDXObjectImage)xobject;
String name = null;
if (addKey)
{
name = getUniqueFileName( prefix + "_" + key, image.getSuffix() );
}
else
{
name = getUniqueFileName( prefix, image.getSuffix() );
}
System.out.println( "Writing image:" + name );
if (directJPEG && "jpg".equals(image.getSuffix()))
{
writeJpeg2file((PDJpeg) image, name);
}
else
{
image.write2file(name);
}
image.clear(); // PDFBOX-2101 get rid of cache ASAP
}
// maybe there are more images embedded in a form object
else if (xobject instanceof PDXObjectForm)
{
PDXObjectForm xObjectForm = (PDXObjectForm)xobject;
PDResources formResources = xObjectForm.getResources();
processResources(formResources, prefix, addKey, directJPEG);
}
}
}
resources.clear();
}
private String getUniqueFileName( String prefix, String suffix )
{
String uniqueName = null;
File f = null;
while( f == null || f.exists() )
{
uniqueName = prefix + "-" + imageCounter;
f = new File( uniqueName + "." + suffix );
imageCounter++;
}
return uniqueName;
}
/**
* This will print the usage requirements and exit.
*/
private static void usage()
{
System.err.println( "Usage: java org.apache.pdfbox.ExtractImages [OPTIONS] <PDF file>\n" +
" -password <password> Password to decrypt document\n" +
" -prefix <image-prefix> Image prefix(default to pdf name)\n" +
" -addkey add the internal image key to the file name\n" +
" -nonSeq Enables the new non-sequential parser\n" +
" -directJPEG Forces the direct extraction of JPEG images regardless of colorspace\n" +
" <PDF file> The PDF document to use\n"
);
System.exit( 1 );
}
}