VB.NET Requires Chilkat v11.7.0+

Remove a Watermark from a PDF

See more PDF Watermark Examples

Demonstrates remove, which deletes the watermarks matching the filter and reports how many went. The filter is the same one list takes, so the usual sequence is to list what is there and then remove by id, by source, or by text. An empty filter is refused unless "all" is true, so that a whole document cannot be stripped by an empty JSON object. Removing finds nothing is not an error: "removed" is simply 0. An annotation is deleted, the marked content of an artifact and any form it alone used are deleted, and the content of a layer goes with the layer once nothing else uses it. A watermark added with the content approach is part of the page and is never removable. 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 acrobat_watermark.pdf

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


Dim filter As New Chilkat.JsonObject
Dim jsonOut As New Chilkat.JsonObject

'  What is in there?  A watermark from another producer is given an id of the form ext1, ext2, ...
success = pdf.Watermark("list",filter,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("watermarks: " & jsonOut.IntOf("count"))
jsonOut.I = 0
Debug.WriteLine("first id: " & jsonOut.StringOf("watermarks[i].id") & " text: " & jsonOut.StringOf("watermarks[i].text"))

'  Add one of our own beside it, so that the filters below have two to choose between.
Dim json As New Chilkat.JsonObject
json.UpdateString("type","text")
json.UpdateString("text","SUPERSEDED")
json.UpdateString("id","superseded")
success = pdf.Watermark("add",json,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  Remove only what Acrobat put there, leaving ours in place.
filter.UpdateString("source","acrobat")
success = pdf.Watermark("remove",filter,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("removed (acrobat): " & jsonOut.IntOf("removed"))

Dim empty As New Chilkat.JsonObject
success = pdf.Watermark("detect",empty,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("left in the document: " & jsonOut.IntOf("count"))

'  An empty filter is refused for remove: say all explicitly to strip everything.
success = pdf.Watermark("remove",empty,jsonOut)
If (success = False) Then
    Debug.WriteLine("An empty filter was refused, as it should be.")
End If

empty.UpdateBool("all",True)
success = pdf.Watermark("remove",empty,jsonOut)
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("removed (all): " & jsonOut.IntOf("removed"))

'  The changes are in memory until the file is written.
success = pdf.WriteFile("qa_output/acrobat_unwatermarked.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If


'  Sample output:

'  watermarks: 1
'  first id: ext1 text: Sample
'  removed (acrobat): 1
'  left in the document: 1
'  An empty filter was refused, as it should be.
'  removed (all): 1