How do I paint the GroupBarItem image without scaling the image in Windows Forms Navigation Pane (GroupBar)

You can draw the image of GroupBarItem (without scaling it), by overriding the DrawGroupBarImage method of the GroupBar.

// For this callback to occur LargeImageMode must be set to true.
 this.groupBarItem1.LargeImageMode = true;

protected override void DrawGroupBarImage(Graphics g, int index, Rectangle bar)
{
Point location = new Point(bar.X + 20, bar.Y);
g.DrawImage(this.VisibleGroupBarItems[index].Image, new Rectangle(location, new Size(20, 20)));
}
' For this callback to occur LargeImageMode must be set to true.

Me.groupBarItem1.LargeImageMode = True

Overrides Sub DrawGroupBarImage(Graphics g, Integer index, Rectangle bar)

Dim location As New Point(bar.X + 20, bar.Y)

g.DrawImage(Me.VisibleGroupBarItems(index).Image, New Rectangle(location, New Size(20, 20)))

End Sub