In Winforms, this is quite clever, it should only look like an extinction. One method is to use Control.DrawToBitmap () to create a bitmap for the control. And then blend from the background bitmap to the foreground bitmap using a timer.
I use UserControl instead of Panel so that you can design the control using the Winforms designer. However, the code will work in any form of control. Add a new class to your project and paste the code shown below. Compilation. Create your own UserControl from this using the Project template + Add New Item, Windows Forms node, “Inherited User Control” and select FadeControl from the popup list. Create a custom control as usual.
As indicated, the control will automatically disappear from the parent BackColor to the control content as soon as you add the control to the parent. Call FadeOut () so that it blends with the background. Pass true if you want to automatically remove the control when it disappears. You can use FadeIn () and the Faded property to manually control fading. You can adjust the numbers in the lines commented out with // tweakable to adjust the animation. Extra work is needed if the parent has an opaque background.
using System; using System.Drawing; using System.Drawing.Imaging; using System.Windows.Forms; class FadeControl : UserControl { public FadeControl() { pbox = new PictureBox(); pbox.BorderStyle = BorderStyle.None; pbox.Paint += new PaintEventHandler(pbox_Paint); fadeTimer = new Timer(); fadeTimer.Interval = 15; // tweakable fadeTimer.Tick += new EventHandler(fadeTimer_Tick); } public bool Faded { get { return blend < 0.5f; } } public void FadeIn() { stopFade(false); createBitmaps(); startFade(1); } public void FadeOut(bool disposeWhenDone) { stopFade(false); createBitmaps(); disposeOnComplete = disposeWhenDone; startFade(-1); } private void createBitmaps() { bmpBack = new Bitmap(this.ClientSize.Width, this.ClientSize.Height); using (var gr = Graphics.FromImage(bmpBack)) gr.Clear(this.Parent.BackColor); bmpFore = new Bitmap(bmpBack.Width, bmpBack.Height); this.DrawToBitmap(bmpFore, this.ClientRectangle); } void fadeTimer_Tick(object sender, EventArgs e) { blend += blendDir * 0.02F; // tweakable bool done = false; if (blend < 0) { done = true; blend = 0; } if (blend > 1) { done = true; blend = 1; } if (done) stopFade(true); else pbox.Invalidate(); } void pbox_Paint(object sender, PaintEventArgs e) { Rectangle rc = new Rectangle(0, 0, pbox.Width, pbox.Height); ColorMatrix cm = new ColorMatrix(); ImageAttributes ia = new ImageAttributes(); cm.Matrix33 = blend; ia.SetColorMatrix(cm); e.Graphics.DrawImage(bmpFore, rc, 0, 0, bmpFore.Width, bmpFore.Height, GraphicsUnit.Pixel, ia); cm.Matrix33 = 1F - blend; ia.SetColorMatrix(cm); e.Graphics.DrawImage(bmpBack, rc, 0, 0, bmpBack.Width, bmpBack.Height, GraphicsUnit.Pixel, ia); } private void stopFade(bool complete) { fadeTimer.Enabled = false; if (complete) { if (!Faded) this.Controls.Remove(pbox); else if (disposeOnComplete) this.Dispose(); } if (bmpBack != null) { bmpBack.Dispose(); bmpBack = null; } if (bmpFore != null) { bmpFore.Dispose(); bmpFore = null; } } private void startFade(int dir) { this.Controls.Add(pbox); this.Controls.SetChildIndex(pbox, 0); blendDir = dir; fadeTimer.Enabled = true; fadeTimer_Tick(this, EventArgs.Empty); } protected override void OnCreateControl() { base.OnCreateControl(); if (!DesignMode) FadeIn(); } protected override void OnResize(EventArgs eventargs) { pbox.Size = this.ClientSize; base.OnResize(eventargs); } protected override void Dispose(bool disposing) { if (disposing) { stopFade(false); pbox.Dispose(); fadeTimer.Dispose(); } base.Dispose(disposing); } private PictureBox pbox; private Timer fadeTimer; private Bitmap bmpBack, bmpFore; private float blend; private int blendDir = 1; private bool disposeOnComplete; }