wxSize panelSize = this->GetSize();

wxMemoryDC memDC;
wxBitmap bitmap(panelSize.GetWidth(), panelSize.GetHeight());

memDC.SelectObject(bitmap);
memDC.SetBackground(*wxWHITE_BRUSH);
memDC.Clear();
wxColour col1, col2, colWhite;
col1.Set(wxT("#2294E1"));
col2.Set(wxT("#000000"));
colWhite.Set(255,255,255,50);
wxBrush transparent(wxColour(255, 255, 255), wxTRANSPARENT);

memDC.GradientFillLinear(wxRect(0, 0, panelSize.GetWidth(), panelSize.GetHeight()), col1, col2, wxNORTH);

memDC.SetBrush(colWhite);
memDC.SetPen(wxPen(col1, 1, wxSOLID));
memDC.DrawRectangle(10, 60, (panelSize.GetWidth()-20), (panelSize.GetHeight()-70));

dc->DrawBitmap(bitmap, wxPoint(0, 0));