DotImage allows users to create PDF files with different compression per frame. The PdfEncoder uses an event SetEncoderCompression. The PdfTranslator has a property which can be assigned a delegate method to do its processing.

PdfEncoder

C#

PdfEncoder pdf = new PdfEncoder();
pdf.SetEncoderCompression += new EncoderCompressionEventHandler(pdf_SetEncoderCompression);
 
void pdf_SetEncoderCompression(object sender, Atalasoft.Imaging.Codec.EncoderCompressionEventArgs e)
{
   if (e.Image.PixelFormat == PixelFormat.Pixel1bppIndexed)
     e.Compression = new PdfCodecCompression(PdfCompressionType.CcittGroup4);
   else
    e.Compression = new PdfCodecCompression(PdfCompressionType.Deflate);
}

VB.NET

     
Dim pdf As New PdfEncoder() 
AddHandler pdf.SetEncoderCompression, AddressOf pdf_SetEncoderCompression
 
Private Sub pdf_SetEncoderCompression(ByVal sender As Object, ByVal e As Atalasoft.Imaging.Codec.EncoderCompressionEventArgs) 
    If e.Image.PixelFormat = PixelFormat.Pixel1bppIndexed Then 
        e.Compression = New PdfCodecCompression(PdfCompressionType.CcittGroup4) 
    End If 
    Else
    e.Compression = New PdfCodecCompression(PdfCompressionType.Deflate) 
    End Else
End Sub

PdfTranslator

C#

PdfTranslator trans = new PdfTranslator();
trans.CompressionSelector = SetCompression;
 
private PdfImageCompressionType SetCompression(PixelFormat pixelformat)
{
     if (pixelformat == PixelFormat.Pixel1bppIndexed)
          return PdfImageCompressionType.CcittGroup4;
     return PdfImageCompressionType.Flate;
}

VB.NET

   
Dim trans As New PdfTranslator() 
trans.CompressionSelector = AddressOf SetCompression
 
Private Function SetCompression(ByVal pixelformat__1 As PixelFormat) As PdfImageCompressionType 
    If pixelformat__1 = PixelFormat.Pixel1bppIndexed Then 
        Return PdfImageCompressionType.CcittGroup4 
    End If 
    Return PdfImageCompressionType.Flate 
End Function

Original Article:
Q10251 - HOWTO: Save a Pdf file with Compression