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。
请注意,相关的PDF对复制内容没有任何限制,至少从我在文档的“文档限制摘要”中看到的内容:它们都允许“内容复制”和“内容复制可访问性” !在同一个PDF文件中,有可选的内容和其他不可选的部分。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!
以下是我用来将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<PDPage> 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
答案 0 :(得分:5)
有问题的两个图像,右上角的fischer徽标和略微向下的小草图,每个都是通过在页面上填充一个带有平铺图案的区域来绘制的,而该平铺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,自动图像提取器通常也不会走 Pattern 资源树。
您可以使用PDFBox轻松构建模式图像提取器,例如对于PDFBox 1.8.10:
public void extractPatternImages(PDDocument document, String fileNameFormat) throws IOException
{
List<PDPage> 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<String, PDPatternResources> patterns = resources.getPatterns();
for (Map.Entry<String, PDPatternResources> 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<String, PDXObject> xObjects = resources.getXObjects();
if (xObjects == null)
return;
for (Map.Entry<String, PDXObject> 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<String, PDXObject> xObjects = resources.getXObjects();
if (xObjects == null)
return;
for (Map.Entry<String, PDXObject> 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<String, PDPatternResources> patterns = resources.getPatterns();
for (Map.Entry<String, PDPatternResources> 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())));
}
我将它应用于您的样本PDF
public void testtestDrJorge() throws IOException
{
try (InputStream resource = getClass().getResourceAsStream("testDrJorge.pdf"))
{
PDDocument document = PDDocument.load(resource);
extractPatternImages(document, "testDrJorge%s.%s");;
}
}
并得到两张图片:
图像丢失了红色部分。这很可能是因为PDFBox版本1.x.x不能正确支持CMYK图像的提取,参见PDFBOX-2128 (CMYK images are not supported correctly),您的图片均为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<COSName> 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<COSName> 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<COSName> 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<COSName> 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));
}
并获取
看起来像是一种改进......;)