in.setFrameBuffer (reinterpret_cast<Imf::Rgba *>(in_surface[0]), 1, w);
in.readPixels (in.dataWindow().min.y, in.dataWindow().max.y);
in.setFrameBuffer (reinterpret_cast<Imf::Rgba *>(in_surface[0]), 1, w);
in.readPixels (in.dataWindow().min.y, in.dataWindow().max.y);