public class TR_Document extends TR_AbstractDrawable {
    
    
    /** Ориентация листа 
     *  PARTRAIT - книжная
     *  LANDSCAPE - альбомная
     */
    public enum DocumentOrientation { PARTRAIT, LANDSCAPE };
    
    private int aDPI = 72;
    private DocumentOrientation orientation = DocumentOrientation.LANDSCAPE;
    // мои попытки привязаться к реальным размерам
    private Dimension size = TR_Utils.mmsToPixels(TR_Utils.A4_PAGE_SIZE_MM, aDPI);
    
    private AffineTransform at = new AffineTransform();
    
    public TR_Document() {
       
    }
    
    
    public TR_Document(Dimension aSize, DocumentOrientation orient) {
        orientation = orient;
        /* если альбомная ориентация листа, то повернём лист(поменяем размеры местами) */
        if(orient == DocumentOrientation.LANDSCAPE) {
            size.width = aSize.height;
            size.height = aSize.width;
        } else
            size = aSize;
    }
    
    public void loadfromFile(String fileName) {}
    
    public void setSize(Dimension s) {
        size.setSize(s);
    }

    @Override
    public Dimension getSize() {
        return new Dimension(size);
    }

    @Override
    public Rectangle getContentBBox() {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
    
    public void setOrientation(DocumentOrientation orient) {
        orientation = orient;
        if(orient == DocumentOrientation.LANDSCAPE) {
            int tmp = size.width;
            size.width = size.height;
            size.height = tmp;
        } 
    }
    

    @Override
    public void draw(Graphics g, double scaleFactor) {
        /*
        Graphics2D g2d = (Graphics2D)g;
        
        AffineTransform old = g2d.getTransform();
        AffineTransform at = new AffineTransform();
        
        g2d.setTransform(at);
        at.translate(50, 50);  // зазор между краем окна и нашей панелью для рисования
        at.scale(scaleFactor, scaleFactor);
        //g2d.scale(scaleFactor, scaleFactor);
        //size.setSize((int)Math.round(size.width * scaleFactor), 
        //             (int)Math.round(size.height * scaleFactor));
        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, size.width, size.height);
        
        g2d.setColor(Color.BLACK);
        g2d.drawRect(0, 0, size.width, size.height);
        
        
        //g2d.setColor(Color.GRAY);
        //g2d.drawRect(0, 0, size.width, size.height);
        
        g2d.setTransform(old);
        g2d.dispose();
        */
    }

public class DrawEx {
    public static void createGUI() {
        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("Draw Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        DrawArea da = new DrawArea();
        frame.getContentPane().add(da, BorderLayout.CENTER);

        frame.setPreferredSize(new Dimension(800, 600));

        frame.pack();
        frame.setVisible(true); 
        frame.setLocationRelativeTo(null);
     }
     
     public static void main(String[] args) {
          javax.swing.SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    createGUI();
               }
          });
     }
}

public class DrawArea extends JComponent {
    
    private int originX = 0; 
    private int originY = 0;
    private int W = 0;
    private int H = 0;
    
    public DrawArea() {
        
    }
    
    
    public void paintComponent(Graphics g) {
        // устанавливаем цвет холста
        Graphics2D g2d = (Graphics2D)g;
        
        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, W, H);
        
        
        // рисуем что-нибудь
        g2d.setColor(Color.DARK_GRAY);
        g2d.drawLine(10, 10, 100, 100);
        
        g2d.drawRect(50, 50, 100, 80);
    }
    
  
    public Dimension getPrefferedSize() {
        //System.out.print("W: " + getWidth() + " H: " + getHeight() + "\n");
        return new Dimension(W, H);
    }
    
    public void setPrefferedSize(Dimension d) {
        super.setPreferredSize(d);
        W = d.width;
        H = d.height;
        System.out.print("W: " + W + " H: " + H);
    }
    
    
}

public class DrawArea extends JComponent {
    private float zoom = 1.0f;
    int lastX = 0;
    int lastY = 0;
    
    int offsetX = 0;
    int offsetY = 0;
    
    public DrawArea() {
        
        addMouseWheelListener(new MouseAdapter() {
            @Override
            public void mouseWheelMoved(MouseWheelEvent e) {
                double delta = 0.075f * e.getPreciseWheelRotation();
                setZoom(getZoom() + (float)delta);
                repaint();
                System.out.print("wheel! Zoom: " + getZoom() + "\n");
            }
        });
        
        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                if(SwingUtilities.isMiddleMouseButton(e)){
                    // capture starting point
                    lastX = e.getX();
                    lastY = e.getY();
                }
            }
        });
        
        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                if(SwingUtilities.isMiddleMouseButton(e)){
                    int dx = e.getX() - lastX;
                    int dy = e.getY() - lastY;
                    
                    offsetX = dx; 
                    offsetY = dy;
                    
                    repaint();
                }
            }
        });
    }
    
    public float getZoom() { return zoom; }
    
    public void setZoom(float value) {
        if(zoom != value) {
            zoom = value;
            
            if(zoom < 0.1) zoom = 0.1f;
            if(zoom > 10) zoom = 10f;
        }
    }
    
    
    @Override
    public void paintComponent(Graphics g) {
        // устанавливаем цвет холста
        Graphics2D g2d = (Graphics2D)g;
        AffineTransform at = new AffineTransform();
        
        at.translate(offsetX, offsetY);
        at.scale(zoom, zoom);
        g2d.setTransform(at);
        
        // рисуем что-нибудь
        g2d.setColor(Color.DARK_GRAY);
        // просто добавляем смещение, надо же как-то мышкой двигать, для примера
        g2d.drawLine(20, 20, 100, 100);
        g2d.drawRect(50, 50, 100, 80);
        
        g2d.dispose();
    }
}