The ImageAttributes object can perform gamma correction. The following code makes an ImageAttributes object and uses its SetGamma method to set a gamma value. It then uses a Graphics object's DrawImage method to draw the original image, passing it the ImageAttributes object to set the image's gamma value.

When you change the program's scroll bar or enter a new value in the TextBox, the program uses this routine to adjust the image's gamma accordingly. The result is quite impressive. The original image is as I scanned it from a photograph. Setting gamma to 0.4 makes the image much brighter and sharper.

Private Sub picResult_Paint(ByVal sender As Object, ByVal e _
    As System.Windows.Forms.PaintEventArgs) Handles _
    picResult.Paint
    Dim pts() As Point = { _
        New Point(0, 0), _
        New Point(picSource.Image.Width - 1, 0), _
        New Point(0, picSource.Image.Height - 1) _
    }
    Dim rect As New Rectangle(0, 0, picSource.Image.Width, _
        picSource.Image.Height)
    Dim image_attr As New ImageAttributes
    Dim gamma As Single = hbarGamma.Value / 10
    image_attr.SetGamma(gamma)
    e.Graphics.DrawImage(picSource.Image, pts, rect, _
        GraphicsUnit.Pixel, image_attr)
End Sub