Private Sub CreateGradient()
  Dim newGraphics As Graphics
  Dim pgb As PathGradientBrush

  Try
    ' Create a new PathGradientBrush, supplying an array of points created 
    ' by calling the GetPoints method.
    pgb = New PathGradientBrush( _
     GetPoints(radius, New Point(radius, radius)))

    ' Set the various properties. Note the SurroundColors property, which 
    ' contains an array of points, in a one-to-one relationship with the 
    ' points that created the gradient.
    pgb.CenterColor = Color.White
    pgb.CenterPoint = New PointF(radius, radius)
    pgb.SurroundColors = GetColors()

    ' Create a new bitmap containing the color wheel gradient, so the 
    ' code only needs to do all this work once. Later code uses the bitmap
    ' rather than recreating the gradient.
    colorImage = New Bitmap( _
     colorRectangle.Width, colorRectangle.Height, _
     PixelFormat.Format32bppArgb)

    newGraphics = Graphics.FromImage(colorImage)
    newGraphics.FillEllipse(pgb, 0, 0, _
     colorRectangle.Width, colorRectangle.Height)

  Finally
    If Not pgb Is Nothing Then
      pgb.Dispose()
    End If
    If Not newGraphics Is Nothing Then
      newGraphics.Dispose()
    End If
  End Try
End Sub

Private Function GetColors() As Color()
  ' Create an array of COLOR_COUNT colors, looping through all the hues 
  ' between 0 and 255, broken into COLOR_COUNT intervals. HSV is 
  ' particularly well suited for this because the only value that changes 
  ' as you create colors is the Hue.
  Dim Colors(COLOR_COUNT - 1) As Color

  Dim i As Integer
  For i = 0 To COLOR_COUNT - 1
    Colors(i) = ColorHandler.HSVtoColor( _
     i * 255 \ COLOR_COUNT, 255, 255)
  Next
  Return Colors
End Function

Private Function GetPoints( _
 ByVal radius As Double, ByVal centerPoint As Point) _
 As Point()

  ' Generate the array of points that describe the locations of the 
  ' COLOR_COUNT colors to be displayed on the color wheel.
  Dim Points(COLOR_COUNT - 1) As Point

  Dim i As Integer
  For i = 0 To COLOR_COUNT - 1
    Points(i) = GetPoint( _
     i * 360 / COLOR_COUNT, radius, centerPoint)
  Next
  Return Points
End Function

Private Function GetPoint( _
 ByVal degrees As Double, _
 ByVal radius As Double, _
 ByVal centerPoint As Point) As Point

  ' Given the center of a circle and its radius, along with the angle 
  ' corresponding to the point, find the coordinates.  In other words, 
  ' convert from polar to rectangular coordinates.
  Dim radians As Double = degrees / DEGREES_PER_RADIAN

  Return New Point( _
   CInt(centerPoint.X + _
    Math.Floor(radius * Math.Cos(radians))), _
   CInt(centerPoint.Y - _
    Math.Floor(radius * Math.Sin(radians))))
End Function

Private Sub DrawLinearGradient(ByVal TopColor As Color)
  ' Given the top color, draw a linear gradient ranging from black to the 
  ' top color. Use the brightness rectangle as the area to fill.
  Dim lgb As LinearGradientBrush

  Try
    lgb = New LinearGradientBrush( _
     brightnessRectangle, TopColor, _
      Color.Black, LinearGradientMode.Vertical)
    g.FillRectangle(lgb, brightnessRectangle)
  Finally
    If Not lgb Is Nothing Then
      lgb.Dispose()
    End If
  End Try
End Sub

Private Sub UpdateDisplay()
  ' Update the gradients, and place the pointers correctly based on 
  ' colors and brightness.

  Dim selectedBrush As Brush

  Try
    ' Draw the "selected color" rectangle.
    selectedBrush = New SolidBrush(selectedColor)

    ' Draw the saved color wheel image.
    g.DrawImage(colorImage, colorRectangle)

    g.FillRectangle( _
     selectedBrush, selectedColorRectangle)

    ' Draw the "brightness" rectangle.
    DrawLinearGradient(fullColor)
    ' Draw the two pointers.
    DrawColorPointer(colorPoint)
    DrawBrightnessPointer(brightnessPoint)

  Finally
    If Not selectedBrush Is Nothing Then
      selectedBrush.Dispose()
    End If
  End Try
End Sub

Private Sub HandleRGBChange( _
 ByVal sender As System.Object, _
 ByVal e As System.EventArgs) _
 Handles nudRed.ValueChanged, nudBlue.ValueChanged, _
 nudGreen.ValueChanged

  ' If the R, G, or B values change, use this code to update the HSV 
  ' values and invalidate the color wheel (so it updates the pointers).
  ' Check the isInUpdate flag to avoid recursive events when you update 
  ' the NumericUpdownControls.
  If Not isInUpdate Then
    changeType = ChangeStyle.RGB
    RGB = New ColorHandler.RGB(CInt(nudRed.Value), _
     CInt(nudGreen.Value), CInt(nudBlue.Value))
    SetHSV(ColorHandler.RGBtoHSV(RGB))
    Me.Invalidate()
  End If
End Sub

Private Sub ColorChooser1_Paint( _
 ByVal sender As Object, _
 ByVal e As PaintEventArgs) Handles MyBase.Paint

  ' Depending on the circumstances, force a repaint
  ' of the color wheel passing different information.
  Select Case changeType
    Case ChangeStyle.HSV
      myColorWheel.Draw(e.Graphics, HSV)
    Case ChangeStyle.MouseMove, ChangeStyle.None
      myColorWheel.Draw(e.Graphics, selectedPoint)
    Case ChangeStyle.RGB
      myColorWheel.Draw(e.Graphics, RGB)
  End Select
End Sub

' Declared in the ColorWheel class:
Private g As Graphics
Private colorRegion As Region
Private brightnessRegion As Region
Private colorImage As Bitmap

Private Sub Dispose() Implements IDisposable.Dispose
  ' Dispose of graphic resources
  If Not colorImage Is Nothing Then
    colorImage.Dispose()
  End If
  If Not colorRegion Is Nothing Then
    colorRegion.Dispose()
  End If
  If Not brightnessRegion Is Nothing Then
    brightnessRegion.Dispose()
  End If
  If Not g Is Nothing Then
    g.Dispose()
  End If
End Sub

pnlSelectedColor.Visible = False
pnlBrightness.Visible = False
pnlColor.Visible = False

' Calculate the coordinates of the three required regions on the form.
Dim SelectedColorRectangle As Rectangle = _
 New Rectangle(pnlSelectedColor.Location, _
 pnlSelectedColor.Size)
Dim BrightnessRectangle As Rectangle = _
 New Rectangle(pnlBrightness.Location, _
 pnlBrightness.Size)
Dim ColorRectangle As Rectangle = _
 New Rectangle(pnlColor.Location, pnlColor.Size)