VB.Net (Visual Basic) How to generate a bitmap, pixel by pixel, then save to .jpg?

Hi there,

I'm writing a simple app that reads an ordered recordset from SQL then visualizes each cell as a unique pixel with shading between 0 and 255 in the alpha layer.  (Basically, I'm creating a raster image as you would find in a GIS).  My app works great for drawing the image to screen (bitmap), but when it saves to .jpg the resulting file contains only 2 colors - dark blue for the "-99.9999" value, and solid red for the <> "-99.9999" values.  I think the problem is related to a step missing between the setting of individual pixels and the "Save to File" command, but I don't really know.  Here's the code:

            '-----------------------------
            'DECLARE Variables
            '-----------------------------
            pictureBox1.Size = New Size(595, 506)
            Me.Controls.Add(pictureBox1)
            Dim flag As New Bitmap(595, 506)

            'Declare .jpg file
            Dim ThisOutput As New Bitmap(596, 507)
            Dim file_name As String = Application.ExecutablePath
            file_name = "filename"

            Dim flagGraphics As Graphics = Graphics.FromImage(flag)
            Dim jpgGraphics As Graphics = Graphics.FromImage(ThisOutput)

            Dim ThisVal As Double = 0.0
            Dim ThisPixVal As Double = 0.0
            Dim Northing As Integer = 0
            Dim Easting As Integer = 0
            
            'READ image data from SQL
            Dim Conn As SqlConnection = OpenConnection()
            Dim Com As SqlCommand = New SqlCommand("SQL_Statement", Conn)
            Dim reader As SqlDataReader = Com.ExecuteReader()

            'Loop thru Image data
            Northing = 0
            Easting = 0
            While reader.Read()

                  ThisVal = reader(0)

                  'Draw the pixel value
                  If ThisVal <> -99.9999 Then

                        ThisPixVal = Math.Round((ThisVal + 8.9475) * 8.3256)' a constant
                        Dim shadowBrush As New SolidBrush(Color.FromArgb(ThisPixVal, Color.Red))
                        flagGraphics.FillRectangle(shadowBrush, Easting, Northing, 1, 1)
                        ThisOutput.SetPixel(Easting, Northing, Color.FromArgb(ThisPixVal, Color.Red))

                  Else

                        flagGraphics.FillRectangle(Brushes.DarkBlue, Easting, Northing, 1, 1)
                        ThisOutput.SetPixel(Easting, Northing, Color.DarkBlue)

                  End If

                  'Increment Easting, Northing
                  Easting = Easting + 1
                  If Easting = 595 Then
                        Easting = 0
                        Northing = Northing + 1
                  End If

            End While

            'Close the reader
            reader.Close()

            'Save to file
            ThisOutput.Save(file_name & ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg)

            'Draw bitmap to screen
            pictureBox1.Image = flag

Looking forward to some help!

--ash