public PictureForm(List <ScreenCaptureSource> sources)
 {
     this.sources = sources;
     this.Height  = 480;
     this.Width   = 640;
     flowLayout.SetBounds(0, 0, 640, 480);
     Controls.Add(flowLayout);
     foreach (ScreenCaptureSource src in sources)
     {
         PictureWithLabel pwl = new PictureWithLabel(src);
         flowLayout.Controls.Add(pwl);
     }
 }