| When the form's Timer fires, the event handler invalidates the drawing area PictureBox. The PictureBox's Paint event handler makes a LinearGradientBrush. The rectangle the gradient covers is slightly larger than the PictureBox's client rectangle. The brush uses the angle m_Theta to determine the gradient's angle. The program fills the PictureBox with the brush. It then updates m_Theta so the gradient rotates next time. Finally the program draws some text over the colored background. |
Private m_Theta As Single = 0
Private m_Delta As Single = 10
Private Sub tmrRotate_Tick(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles tmrRotate.Tick
picCanvas.Invalidate()
End Sub
Private Sub picCanvas_Paint(ByVal sender As Object, ByVal e _
As System.Windows.Forms.PaintEventArgs) Handles _
picCanvas.Paint
Dim rect As New Rectangle(-3, -3, _
picCanvas.ClientSize.Width + 6, _
picCanvas.ClientSize.Height + 6)
Dim br As New LinearGradientBrush(rect, Color.Red, _
Color.Blue, m_Theta)
e.Graphics.Clear(picCanvas.BackColor)
e.Graphics.FillRectangle(br, Me.ClientRectangle)
br.Dispose()
m_Theta += m_Delta
Dim string_format As New StringFormat
string_format.Alignment = StringAlignment.Center
string_format.LineAlignment = StringAlignment.Center
e.Graphics.DrawString("Some Text", Me.Font, _
Brushes.Black, _
picCanvas.ClientSize.Width \ 2, _
picCanvas.ClientSize.Height \ 2, _
string_format)
End Sub
Download Source Code here
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