tester.get_chain()->add_effect(new OverlayEffect(), input1, input2);
tester.run(out_data, GL_BGRA, COLORSPACE_sRGB, GAMMA_LINEAR);
tester.get_chain()->add_effect(new OverlayEffect(), input1, input2);
tester.run(out_data, GL_BGRA, COLORSPACE_sRGB, GAMMA_LINEAR);