DrawToBitmap makes a blurry image

I am using GDI+ to draw the initial image on PictureBox - which renders a clean image. I am trying to then capture that drawing and draw it on a PDF using PDFSharp which works, but comes out blurry. I am sure it has something to do with the fact I have changed the destination Rectangle's size. What do i need to do to clean it up?

Code:

Dim bmp As New Bitmap(pb.Width, pb.Height)
Dim pdf As New PdfDocument
Dim page As PdfPage = pdf.AddPage
Dim g As XGraphics = XGraphics.FromPdfPage(page)
pb.DrawToBitmap(bmp, New Rectangle(pb.ClientRectangle.X, pb.ClientRectangle.Y, pb.Width, pb.Height + 20))
g.SmoothingMode = XSmoothingMode.AntiAlias
g.DrawImage(bmp, New XRect(New RectangleF(20, 0, 600, 800)))
pdf.Save(_path)

Solution

It's the anti-aliasing that makes images blurry. AFAIK Adobe Reader draws images with anti-aliasing when used with PDFsharp.

With PDFsharp create an XImage from your BMP and then set

image.Interpolate = false;

for that XImage. This will give a hint to Adobe Reader that anti-aliasing is not wanted for that image.

With respect to screen shots, anti-aliasing is useful when scaling down (e.g. when taking a 400x300 bitmap from an 800x600 screen), but not when scaling up (like Adobe Reader will do with images embedded in PDF files).