var
 pbRect: TRect;
 BitMap:TBitMap;
begin
 pbRect := Rect(0, 0, PaintBox1.Width, PaintBox1.Height);
 BitMap := TBitMap.Create;
 try
  Bitmap.Width := PaintBox1.Width;
  Bitmap.Height := PaintBox1.Height;
  BitMap.Canvas.CopyRect(pbRect, PaintBox1.Canvas, pbRect);
  ClipBoard.Assign(BitMap);
 finally
  BitMap.Free;
 end;
end;