如何使用iText以正确的顺序从PDF中提取图像？

Question

我试图从PDF文件中提取图像.我在网上找到了一个很好的例子:

    PdfReader reader;

    File file = new File("example.pdf");
    reader = new PdfReader(file.getAbsolutePath());
    for (int i = 0; i < reader.getXrefSize(); i++) {
        PdfObject pdfobj = reader.getPdfObject(i);
        if (pdfobj == null || !pdfobj.isStream()) {
            continue;
        }
        PdfStream stream = (PdfStream) pdfobj;
        PdfObject pdfsubtype = stream.get(PdfName.SUBTYPE);
        if (pdfsubtype != null && pdfsubtype.toString().equals(PdfName.IMAGE.toString())) {
            byte[] img = PdfReader.getStreamBytesRaw((PRStream) stream);
            FileOutputStream out = new FileOutputStream(new File(file.getParentFile(), String.format("%1$05d", i) + ".jpg"));
            out.write(img);
            out.flush();
            out.close();
        }
    }

这给了我所有的图像,但图像的顺序错误.我的下一次尝试看起来像这样:

for (int i = 0; i <= reader.getNumberOfPages(); i++) {
  PdfDictionary d = reader.getPageN(i);
  PdfIndirectReference ir = d.getAsIndirectObject(PdfName.CONTENTS);
  PdfObject o = reader.getPdfObject(ir.getNumber());
  PdfStream stream = (PdfStream) o;
  // rest from example above
}

虽然o.isStream()== true,但我只得到/ Length和/ Filter,并且流只有大约100个字节长.根本找不到图像.

我的问题是如何以正确的顺序从PDF文件中获取所有图像的正确方法.

Answer 1

我在其他地方找到了答案，即 iText 邮件列表。

以下代码适用于我 - 请注意我切换到PdfBox：

PDDocument document = null; 
document = PDDocument.load(inFile); 
List pages = document.getDocumentCatalog().getAllPages();
Iterator iter = pages.iterator(); 
while (iter.hasNext()) {
            PDPage page = (PDPage) iter.next();
            PDResources resources = page.getResources();
            Map pageImages = resources.getImages();
            if (pageImages != null) { 
                Iterator imageIter = pageImages.keySet().iterator();
                while (imageIter.hasNext()) {
                    String key = (String) imageIter.next();
                    PDXObjectImage image = (PDXObjectImage) pageImages.get(key);
                    image.write2OutputStream(/* some output stream */);
                }
            }
}