Java - Contacto EXACTO entre el mouse y un JButton

boton1.setBorder(null);

boton1. setContentAreaFilled(false);

ImageIcon imagenboton1 = new ImageIcon("src/modo_prueba/arboll.png");

boton1.setIcon(imagenboton1);

public class Temporal {

    public static void main(String[] args) {

        interfaz ventana = new interfaz();

    }

}

class interfaz extends JFrame

{

    public interfaz()

    {

        setVisible(true);

        setBounds(20,20,600,400);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setTitle("MI APLICACION");

        add(new lamina());

    }

}

class lamina extends JPanel

{

    Color micolor;

    lamina()

    {

        setLayout(null);

        JButton boton1 = new JButton();

        add(boton1);

        boton1.setBorderPainted(false);

        boton1.setContentAreaFilled(false);

        boton1.setBounds(0, 0, 400, 250);

        boton1.addMouseListener(new mouse());

        ImageIcon imagenboton1 = new ImageIcon("src/temporal/arboll.png");

        boton1.setIcon(imagenboton1);

    }

    class mouse extends MouseAdapter

    {

        @Override

        public void mousePressed(MouseEvent e)

        {

            try {

                micolor = new Robot().getPixelColor(e.getXOnScreen(), e.getYOnScreen());

                System.out.println("R: "+micolor.getRed()+" G: "+micolor.getGreen() + " B: " + micolor.getBlue()+ " A: "+ micolor.getAlpha());

            } catch (AWTException ex) {

                Logger.getLogger(lamina.class.getName()).log(Level.SEVERE, null, ex);

            }

        }

    }

}

public class Test1 extends JFrame {

	/* */

	Test1() throws IOException {

		super("Test png button");

		setDefaultCloseOperation(EXIT_ON_CLOSE);

		createMain(getContentPane());

		pack();

	}

	/* */

	void createMain(Container p) throws IOException {

		ImageIcon test = new ImageIcon("/tmp/tbrn2c08.png");

		p.add(new MyButton(test));

	}

	/* */

	public static void main(String[] args) throws IOException {

		new Test1().setVisible(true);

	}

	/* */

	class MyButton extends JButton {

		BufferedImage ii;

		/* */

		MyButton(ImageIcon i) {

			super(i);

			ii = new BufferedImage(i.getIconWidth(), i.getIconHeight(), BufferedImage.TYPE_INT_ARGB);

			ii.getGraphics().drawImage(i.getImage(), 0, 0, null);

			setOpaque(true);

			setContentAreaFilled(false);

			setBorderPainted(false);

			setFocusPainted(false);

			addMouseMotionListener(new MouseAdapter() {

				@Override

				public void mouseMoved(MouseEvent e) {

					if(testOpacityUnderPos(e.getX(), e.getY())) {

						// Do some effect

					} else {

						// undo effect

					}

				}

			});

			addMouseListener(new MouseAdapter() {

				@Override

				public void mouseClicked(MouseEvent e) {

					if(testOpacityUnderPos(e.getX(), e.getY())) {

						System.out.println("Image Clicked !");

					}

				}

			});

		}

		/* */

		private boolean testOpacityUnderPos(int x, int y) {

			Icon test = getIcon();

			int ix = (getWidth() - test.getIconWidth()) / 2;

			int iy = (getHeight() - test.getIconHeight()) / 2;

			if((x > ix) && (x < (ix + test.getIconWidth()))) {

				if((y > iy) && (y < (iy + test.getIconHeight()))) {

					int rgb = ii.getRGB(x - ix, y - iy);

					if((rgb & 0xff000000) != 0) {

						return true;

					}

				}

			}

			return false;

		}

	}

}