Hello, please help me figure out how to modify image color (brightness,
gamma, contrast, RGB....whatever can be modified) inside a PDF.
I have the following code which works without an error, the part I need help
with is marked {.....what to do here ....}
thank you very much in advance.
Hakan
Imports iTextSharp
Imports iTextSharp.text
Imports iTextSharp.text.pdf
Imports System.IO
Dim reader As PdfReader = New pdf.PdfReader("c:\testfile.pdf")
Dim pdfObj As PdfObject
Dim pdfdict As PdfStream
Dim pdfsubtype As PdfObject
Dim pdfcolorspace As PdfObject
For i As Integer = 0 To reader.XrefSize - 1
pdfObj = reader.GetPdfObject(i)
If pdfObj IsNot Nothing Then
If pdfObj.IsStream Then
pdfdict = DirectCast(pdfObj, PdfStream)
pdfsubtype = pdfdict.Get(PdfName.SUBTYPE)
If pdfsubtype IsNot Nothing Then
If Not pdfsubtype.ToString.Equals(PdfName.IMAGE.ToString) Then Continue For
pdfcolorspace = pdfdict.Get(PdfName.COLORSPACE)
If pdfcolorspace.ToString.Equals(PdfName.DEVICERGB.ToString) Then
'here is where it gets exciting....
'comment.. this code catches the single image that is in the original PDF
and returns DEVICERGB...debug confirms this code block executes as expected
'{...help needed here onwards ....what kind of action do I have to take to
set a new image property like different brightness, gamma, RGB values
etc....eventually a user will look at the PDF and change values a couple of
times making the PDF darker or lighter etc....}
....
...
..
'Im guessing I need something like...
pdfdict.Put(PdfName.COLORSPACE, {....what do I need to prepare for this
....})
'finally write back to a new pdf
Dim stp As PdfStamper = New PdfStamper(reader, New IO.FileStream(
"C:\output.pdf", IO.FileMode.Create))
stp.Close()
reader.Close()
' ....at the moment the outcoming PDF is identical to the original..as
expect, no errors or warnings
End
End If
End If
End If
End If
Next
reader.Close()
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