我正在使用Apache PDFBox从PDF文件中提取页面,我找不到提取不可选内容(文本或图像)的方法.使用可从PDF文件中选择的内容,没有问题.
需要注意的是有问题的PDF文件不具有任何限制关于复制的内容,至少从我上的文件的"文档限制小结"看到:它们都具有"内容复制"和"内容复制为Accessbility"不允许的!在同一PDF文件中,有可选择的内容和不可选择的其他部分.所发生的是,提取的页面带有"洞",即它们只有PDF的可选部分.但是在MS Word上,如果我将PDF添加为对象,则会显示PDF页面的全部内容!所以我希望对PDFBox lib或任何其他Java lib做同样的事情!
这是我用来将PDF页面转换为图像的代码:
private void convertPdfToImage(File pdfFile, int pdfId) throws IOException {
PDDocument document = PDDocument.loadNonSeq(pdfFile, null);
List pdPages = document.getDocumentCatalog().getAllPages();
for (PDPage pdPage : pdPages) {
BufferedImage bim = pdPage.convertToImage(BufferedImage.TYPE_INT_RGB, 300);
ImageIOUtil.writeImage(bim, TEMP_FILEPATH + pdfId + ".png", 300);
}
document.close();
}
有没有办法从这个Apache PDFBox库(或任何其他类似的库)中提取PDF中的不可选内容？或者这根本不可能？如果确实不是,为什么呢？
非常感谢任何帮助!
编辑:我使用Adobe Reader作为PDF查看器和PDFBox v1.8.以下是PDF示例:https://dl.dropboxusercontent.com/u/2815529/test.pdf
所讨论的两个图像,右上角的fischer徽标和略微向下的小草图,每个都是通过用页面图案填充页面上的区域来绘制的,而该图案又在其内容流中绘制相应的图像.
Adobe Reader不允许选择模式的内容,并且自动图像提取器通常也不会遍历Pattern资源树.
您可以使用PDFBox轻松构建模式图像提取器,例如PDFBox 1.8.10:
public void extractPatternImages(PDDocument document, String fileNameFormat) throws IOException
{
List pages = document.getDocumentCatalog().getAllPages();
if (pages == null)
return;
for (int i = 0; i < pages.size(); i++)
{
String pageFormat = String.format(fileNameFormat, "-" + i + "%s", "%s");
extractPatternImages(pages.get(i), pageFormat);
}
}
public void extractPatternImages(PDPage page, String pageFormat) throws IOException
{
PDResources resources = page.getResources();
if (resources == null)
return;
Map patterns = resources.getPatterns();
for (Map.Entry patternEntry : patterns.entrySet())
{
String patternFormat = String.format(pageFormat, "-" + patternEntry.getKey() + "%s", "%s");
extractPatternImages(patternEntry.getValue(), patternFormat);
}
}
public void extractPatternImages(PDPatternResources pattern, String patternFormat) throws IOException
{
COSDictionary resourcesDict = (COSDictionary) pattern.getCOSDictionary().getDictionaryObject(COSName.RESOURCES);
if (resourcesDict == null)
return;
PDResources resources = new PDResources(resourcesDict);
Map xObjects = resources.getXObjects();
if (xObjects == null)
return;
for (Map.Entry entry : xObjects.entrySet())
{
PDXObject xObject = entry.getValue();
String xObjectFormat = String.format(patternFormat, "-" + entry.getKey() + "%s", "%s");
if (xObject instanceof PDXObjectForm)
extractPatternImages((PDXObjectForm)xObject, xObjectFormat);
else if (xObject instanceof PDXObjectImage)
extractPatternImages((PDXObjectImage)xObject, xObjectFormat);
}
}
public void extractPatternImages(PDXObjectForm form, String imageFormat) throws IOException
{
PDResources resources = form.getResources();
if (resources == null)
return;
Map xObjects = resources.getXObjects();
if (xObjects == null)
return;
for (Map.Entry entry : xObjects.entrySet())
{
PDXObject xObject = entry.getValue();
String xObjectFormat = String.format(imageFormat, "-" + entry.getKey() + "%s", "%s");
if (xObject instanceof PDXObjectForm)
extractPatternImages((PDXObjectForm)xObject, xObjectFormat);
else if (xObject instanceof PDXObjectImage)
extractPatternImages((PDXObjectImage)xObject, xObjectFormat);
}
Map patterns = resources.getPatterns();
for (Map.Entry patternEntry : patterns.entrySet())
{
String patternFormat = String.format(imageFormat, "-" + patternEntry.getKey() + "%s", "%s");
extractPatternImages(patternEntry.getValue(), patternFormat);
}
}
public void extractPatternImages(PDXObjectImage image, String imageFormat) throws IOException
{
image.write2OutputStream(new FileOutputStream(String.format(imageFormat, "", image.getSuffix())));
}
(ExtractPatternImages.java)
我将它应用到您的样本PDF中
public void testtestDrJorge() throws IOException
{
try (InputStream resource = getClass().getResourceAsStream("testDrJorge.pdf"))
{
PDDocument document = PDDocument.load(resource);
extractPatternImages(document, "testDrJorge%s.%s");;
}
}
(ExtractPatternImages.java)
并得到两个图像:
`testDrJorge-O-R15-R14.png
testDrJorge-0-R38-R37.png
图像丢失了红色部分.这很可能是因为PDFBox版本1.xx不能正确支持CMYK图像的提取,参见 PDFBOX-2128(未正确支持CMYK图像),并且您的图像为CMYK.
我将代码更新为PDFBox 2.0.0(目前仅作为候选版本提供):
public void extractPatternImages(PDDocument document, String fileNameFormat) throws IOException
{
PDPageTree pages = document.getDocumentCatalog().getPages();
if (pages == null)
return;
for (int i = 0; i < pages.getCount(); i++)
{
String pageFormat = String.format(fileNameFormat, "-" + i + "%s", "%s");
extractPatternImages(pages.get(i), pageFormat);
}
}
public void extractPatternImages(PDPage page, String pageFormat) throws IOException
{
PDResources resources = page.getResources();
if (resources == null)
return;
Iterable patternNames = resources.getPatternNames();
for (COSName patternName : patternNames)
{
String patternFormat = String.format(pageFormat, "-" + patternName + "%s", "%s");
extractPatternImages(resources.getPattern(patternName), patternFormat);
}
}
public void extractPatternImages(PDAbstractPattern pattern, String patternFormat) throws IOException
{
COSDictionary resourcesDict = (COSDictionary) pattern.getCOSObject().getDictionaryObject(COSName.RESOURCES);
if (resourcesDict == null)
return;
PDResources resources = new PDResources(resourcesDict);
Iterable xObjectNames = resources.getXObjectNames();
if (xObjectNames == null)
return;
for (COSName xObjectName : xObjectNames)
{
PDXObject xObject = resources.getXObject(xObjectName);
String xObjectFormat = String.format(patternFormat, "-" + xObjectName + "%s", "%s");
if (xObject instanceof PDFormXObject)
extractPatternImages((PDFormXObject)xObject, xObjectFormat);
else if (xObject instanceof PDImageXObject)
extractPatternImages((PDImageXObject)xObject, xObjectFormat);
}
}
public void extractPatternImages(PDFormXObject form, String imageFormat) throws IOException
{
PDResources resources = form.getResources();
if (resources == null)
return;
Iterable xObjectNames = resources.getXObjectNames();
if (xObjectNames == null)
return;
for (COSName xObjectName : xObjectNames)
{
PDXObject xObject = resources.getXObject(xObjectName);
String xObjectFormat = String.format(imageFormat, "-" + xObjectName + "%s", "%s");
if (xObject instanceof PDFormXObject)
extractPatternImages((PDFormXObject)xObject, xObjectFormat);
else if (xObject instanceof PDImageXObject)
extractPatternImages((PDImageXObject)xObject, xObjectFormat);
}
Iterable patternNames = resources.getPatternNames();
for (COSName patternName : patternNames)
{
String patternFormat = String.format(imageFormat, "-" + patternName + "%s", "%s");
extractPatternImages(resources.getPattern(patternName), patternFormat);
}
}
public void extractPatternImages(PDImageXObject image, String imageFormat) throws IOException
{
String filename = String.format(imageFormat, "", image.getSuffix());
ImageIOUtil.writeImage(image.getOpaqueImage(), "png", new FileOutputStream(filename));
}
得到
testDrJorge-0-COSName{R15}-COSName{R14}.png
testDrJorge-0-COSName{R38}-COSName{R37}.png
看起来像一个改进......;)
京公网安备 11010802040832号 | 京ICP备19059560号-6 
