I need to extract text from pdf files using iText.
The problem is: some pdf files contain 2 columns and when I extract text I get a text file where columns are merged as the result (i.e. text from both columns in the same line)
this is the code:
public class pdf
{
private static String INPUTFILE = "http://www.revuemedecinetropicale.com/TAP_519-522_-_AO_07151GT_Rasoamananjara__ao.pdf" ;
private static String OUTPUTFILE = "c:/new3.pdf";
public static void main(String[] args) throws DocumentException, IOException {
Document document = new Document();
PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(OUTPUTFILE));
document.open();
PdfReader reader = new PdfReader(INPUTFILE);
int n = reader.getNumberOfPages();
PdfImportedPage page;
// Go through all pages
for (int i = 1; i <= n; i++) {
page = writer.getImportedPage(reader, i);
Image instance = Image.getInstance(page);
document.add(instance);
}
document.close();
PdfReader readerN = new PdfReader(OUTPUTFILE);
for (int i = 1; i <= n; i++) {
String myLine = PdfTextExtractor.getTextFromPage(readerN,i);
System.out.println(myLine);
try {
FileWriter fw = new FileWriter("c:/yo.txt",true);
fw.write(myLine);
fw.close();
}catch (IOException ioe) {ioe.printStackTrace(); }
}
}
Could you please help me with the task?
I am the author of the iText text extraction sub-system. What you need to do is develop your own text extraction strategy (if you look at how PdfTextExtractor.getTextFromPage
is implemented, you will see that you can provide a pluggable strategy).
How you are going to determine where columns start and stop is entirely up to you - this is a difficult problem - PDF doesn't have any concept of columns (heck, it doesn't even have a concept of words - just putting together the text extraction that the default strategy provides is quite tricky). If you know in advanced where the columns are, then you can use a region filter on the text render listener callback (there is code in the iText library for doing this, and the latest version of the iText In Action book gives a detailed example).
If you need to obtain columns from arbitrary data, you've got some algorithm work ahead of you (if you get something working, I'd love to take a look). Some ideas on how to approach this:
Another approach that may be equally feasible would be to analyze draw operations and look for long horizontal and vertical lines (assuming the columns are demarcated in a table-like format). Right now, the iText content parser doesn't have callbacks for these operations, but it would be possible to add them without major difficulty.