How to extract text from a PDF and decode characters?

问题

I am using itextsharp to extract text from a pdf document using this code:

public static bool does_document_text_have_keyword(string keyword, 
                       string pdf_src, Report report_object)  // TEST
{
    try
    {
        PdfReader pdfReader = new PdfReader(pdf_src);
        string currentText;
        int count = pdfReader.NumberOfPages;
        for (int page = 1; page <= count; page++)
        {
           ITextExtractionStrategy strategy = new SimpleTextExtractionStrategy();
           currentText = PdfTextExtractor.GetTextFromPage
                           (pdfReader, page, strategy);
           currentText = Encoding.UTF8.GetString
                           (ASCIIEncoding.Convert
                             (Encoding.Default,                                 
                              Encoding.UTF8, 
                              Encoding.Default.GetBytes(currentText)));

           report_object.log(currentText);  // TEST

           if (currentText.IndexOf
                (keyword, StringComparison.OrdinalIgnoreCase) != -1) return true;
        }
        pdfReader.Close();
        return false;
    }
    catch
    {
        return false;
    }
}

But the problem is, when I extract text, the text has no white spaces, it's as if the white spaces has been replaced with an empty string. Yet in the pdf document, there are white spaces in it. Does anyone know whats happening here?

回答1:

I believe your issue is the SimpleTextExtractionStrategy. From the API documentation at http://api.itextpdf.com/itext/com/itextpdf/text/pdf/parser/SimpleTextExtractionStrategy.html

If the PDF renders text in a non-top-to-bottom fashion, this will result in the text not being a true representation of how it appears in the PDF. This renderer also uses a simple strategy based on the font metrics to determine if a blank space should be inserted into the output.

Try using the LocationTextExtractionStrategy. It's documentation states:

A text extraction renderer that keeps track of relative position of text on page The resultant text will be relatively consistent with the physical layout that most PDF files have on screen.

来源：https://stackoverflow.com/questions/13976233/how-to-extract-text-from-a-pdf-and-decode-characters

标签

pdf

itextsharp