Fade TabPage between TabControl's tab selection

roshihans

After searching on the internet, the possible solution that come out is by using TabPage.DrawToBitmap, put the bitmap in a PictureBox, set the position of PictureBox to the same location of TabPage, and fade it. The code is below :

System::Void tabControl1_SelectedIndexChanged(System::Object^ sender, System::EventArgs^ e)
{
alphaBlend = 250;
repaint = true;

// set TabPicture visibility, location, and size
TabPictureBox->Visible = true;
int posX = tabControl1->Location.X + tabControl1->TabPages\[tabControl1->SelectedIndex\]->Margin.Left + 1;
int posY = tabControl1->Location.Y + tabControl1->ItemSize.Height + 1 + 
	tabControl1->TabPages\[tabControl1->SelectedIndex\]->Margin.Top;
TabPictureBox->Location = System::Drawing::Point(posX, posY);
TabPictureBox->Size = tabControl1->TabPages\[tabControl1->SelectedIndex\]->Size;

// set Bitmap
TabBitmap = gcnew Bitmap(tabControl1->TabPages\[tabControl1->SelectedIndex\]->Width, 
	tabControl1->TabPages\[tabControl1->SelectedIndex\]->Height);			
tabControl1->TabPages\[tabControl1->SelectedIndex\]->DrawToBitmap(TabBitmap,
		Rectangle(0, 0, tabControl1->TabPages\[tabControl1->SelectedIndex\]->Width, 
			tabControl1->TabPages\[tabControl1->SelectedIndex\]->Height));

while (alphaBlend > 0)
{				
	alphaBlend = alphaBlend - 25;
	TabPictureBox->Refresh();
}

TabPictureBox->Visible = false;
repaint = false;

}

System::Void TabPictureBox_Paint(System::Object^ sender, System::Windows::Forms::PaintEventArgs^ e)
{
if (repaint)
{
if (TabBitmap != nullptr)
{
Bitmap^ temp = gcnew Bitmap(TabBitmap);
Graphics^ bitmapGraphics = Graphics::FromImage(temp);
if (alphaBlend < 0) alphaBlend = 0;
SolidBrush^ greyBrush = gcnew SolidBrush(Color::FromArgb(alphaBlend, Color::White));
bitmapGraphics->CompositingMode = CompositingMode::SourceOver;
bitmapGraphics->FillRectangle(greyBrush, Rectangle(0, 0, TabBitmap->Width, TabBitmap->Height));
e->Graphics->CompositingQuality = CompositingQuality::GammaCorrected;
e->Graphics->DrawImage(temp, 0, 0);
}
}
}

The problem is that each time I select the tabPage, my CPU usage spike to 70 - 80% and the fading effect is kind of slow. Is there any solution to fix it so that I can draw the bitmap faster and with minimum CPU usage (less than 50%)? Thanks.