VB.NET Requires Chilkat v11.7.0+

Expand Ligatures and Normalize Unicode in Extracted PDF Text

See more PDF Text Extraction Examples

Demonstrates the "expandLigatures" and "normalize" clean-up options. Typeset PDFs use single glyphs for "fi" and "fl"; by default they are expanded to their letters. Unicode normalization is NFC by default; NFKC also folds compatibility characters such as circled digits, the trademark sign and vulgar fractions into plain characters, and "none" leaves the text as the PDF has it. VB.NET

Dim success As Boolean = False

'  This example requires the Chilkat API to have been previously unlocked.
'  See Global Unlock Sample for sample code.

'  The PDF used in this example is available at ligatures.pdf

Dim pdf As New Chilkat.Pdf
success = pdf.LoadFile("qa_data/pdf/ligatures.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


Dim json As New Chilkat.JsonObject
Dim jsonOut As New Chilkat.JsonObject

'  The first line is set with the fi and fl ligature glyphs; the second has circled digits,
'  a trademark sign and a vulgar fraction.
success = pdf.ExtractText("text",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("---- default (expandLigatures: true, normalize: NFC) ----")
Debug.WriteLine(jsonOut.StringOf("text"))

'  Keep the ligature characters as they are in the PDF.
json.UpdateBool("expandLigatures",False)
json.UpdateString("normalize","none")
success = pdf.ExtractText("text",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("---- expandLigatures: false, normalize: none ----")
Debug.WriteLine(jsonOut.StringOf("text"))

'  NFKC folds the compatibility characters too (and expands ligatures on its own).
json.UpdateString("normalize","NFKC")
success = pdf.ExtractText("text",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("---- normalize: NFKC ----")
Debug.WriteLine(jsonOut.StringOf("text"))

'  Sample output (shown here in ASCII: (fi) and (fl) stand for the single ligature characters, (1) and (2) for the circled digits,
'  (TM) for the trademark sign and 1/2 for the vulgar fraction; the NFKC output has plain "1", "2", "TM" and "1", fraction slash, "2"):

'  ---- default (expandLigatures: true, normalize: NFC) ----
'  Typeset Text
'  
'  The final flight of the season was officially confirmed on the fifth. Rooms (1) and (2) are reserved; the Harbor Cafe(TM) serves 1/2 portions.
'  ---- expandLigatures: false, normalize: none ----
'  Typeset Text
'  
'  The (fi)nal (fl)ight of the season was of(fi)cially con(fi)rmed on the (fi)fth. Rooms (1) and (2) are reserved; the Harbor Cafe(TM) serves 1/2 portions.
'  ---- normalize: NFKC ----
'  Typeset Text
'  
'  The final flight of the season was officially confirmed on the fifth. Rooms 1 and 2 are reserved; the Harbor CafeTM serves 1/2 portions.