wxwidgets绘制不透明度位图

void YourCustomWindow::OnPaint( wxPaintEvent& event ) {
  wxPaintDC dc(this);
  wxImage image( width, height ); 
  image.InitAlpha();
  unsigned char* imgdata = img.GetData();
  unsigned char* imgalpha = img.GetAlpha();


  // manipulate raw memory buffers to populate
  // them with whatever image you like.
  // Putting zeros everywhere will create a fully
  // transparent image.


     // almost done, but not quite... 
     // wxDC can only draw wxBitmaps, not wxImage,
     // so one last step is required
  //
  wxBitmap bmp( image );
  dc.DrawBitmap( bmp, 0, 0 );
 }