final GLReadBufferUtil screenshot = new GLReadBufferUtil(true, false);
    GLCapabilities caps = new GLCapabilities(GLProfile
                .get(GLProfile.GL2ES2));
    //caps.setAlphaBits(1);
    caps.setRedBits(8);
    caps.setGreenBits(8);
    caps.setBlueBits(8);
    caps.setOnscreen(false);
    caps.setPBuffer(true);
    Display display = NewtFactory.createDisplay(null);
    Screen screen = NewtFactory.createScreen(display, 0);
    Window window = NewtFactory.createWindow(screen, caps);
    GLWindow glWindow = GLWindow.create(window);
    glWindow.setSize(256, 256);
    glWindow.setVisible(true);
    glWindow.addGLEventListener(new GLEventListener() {

        @Override
        public void reshape(GLAutoDrawable drawable, int x, int y, int width,
            int height) {
        }

        @Override
        public void init(GLAutoDrawable drawable) {
        GL2ES2 gl = drawable.getGL().getGL2ES2();
        gl.glClearColor(0, 1, 0, 1);
        }

        @Override
        public void dispose(GLAutoDrawable drawable) {

        }

        @Override
        public void display(GLAutoDrawable drawable) {
        GL gl = drawable.getGL();
        gl.glClear(GL.GL_COLOR_BUFFER_BIT);
        gl.glFinish();
        if(screenshot.readPixels(gl, false)) {
            screenshot.write(new File("test.png"));
        }
        }
    });
    glWindow.display();