C# 使用 PdfSharp 从 PDF 中提取文本

Question

Is there a possibility to extract plain text from a PDF-File with PdfSharp? I don't want to use iTextSharp because of its license.

Answer 1

Took Sergio's answer and made some extension methods. I also changed the accumulation of strings into an iterator.

public static class PdfSharpExtensions
{
    public static IEnumerable<string> ExtractText(this PdfPage page)
    {       
        var content = ContentReader.ReadContent(page);      
        var text = content.ExtractText();
        return text;
    }   

    public static IEnumerable<string> ExtractText(this CObject cObject)
    {   
        if (cObject is COperator)
        {
            var cOperator = cObject as COperator;
            if (cOperator.OpCode.Name== OpCodeName.Tj.ToString() ||
                cOperator.OpCode.Name == OpCodeName.TJ.ToString())
            {
                foreach (var cOperand in cOperator.Operands)
                    foreach (var txt in ExtractText(cOperand))
                        yield return txt;   
            }
        }
        else if (cObject is CSequence)
        {
            var cSequence = cObject as CSequence;
            foreach (var element in cSequence)
                foreach (var txt in ExtractText(element))
                    yield return txt;
        }
        else if (cObject is CString)
        {
            var cString = cObject as CString;
            yield return cString.Value;
        }
    }
}

Answer 2

I have implemented it somehow similar to how David did it. Here is my code:

...
{
    // ....
    var page = document.Pages[1];
    CObject content = ContentReader.ReadContent(page);
    var extractedText = ExtractText(content);
    // ...
}

private IEnumerable<string> ExtractText(CObject cObject)
{
    var textList = new List<string>();
    if (cObject is COperator)
    {
        var cOperator = cObject as COperator;
        if (cOperator.OpCode.Name == OpCodeName.Tj.ToString() ||
            cOperator.OpCode.Name == OpCodeName.TJ.ToString())
        {
            foreach (var cOperand in cOperator.Operands)
            {
                textList.AddRange(ExtractText(cOperand));
            }
        }
    }
    else if (cObject is CSequence)
    {
        var cSequence = cObject as CSequence;
        foreach (var element in cSequence)
        {
            textList.AddRange(ExtractText(element));
        }
    }
    else if (cObject is CString)
    {
        var cString = cObject as CString;
        textList.Add(cString.Value);
    }
    return textList;
}

Answer 3

PDFSharp provides all the tools to extract the text from a PDF. Use the ContentReader class to access the commands within each page and extract the strings from TJ/Tj operators.

I've uploaded a simple implementation to github .