Question

I have a problem with 2D transformation program

I have the source code

import java.awt.*;
import java.awt.geom.Line2D;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class House extends JPanel {

    MyCanvas canvas;
    JSlider sliderTransX, sliderTransY, sliderRotateTheta, sliderRotateX,
        sliderRotateY, sliderScaleX, sliderScaleY, sliderWidth;
    double transX = 0.0;
    double transY = 0.0;
    double rotateTheta = 0.0;
    double rotateX = 150.0;
    double rotateY = 150.0;
    double scaleX = 1.0;
    double scaleY = 1.0;
    float width = 1.0f;

    public House() {
        super(new BorderLayout());
        JPanel controlPanel = new JPanel(new GridLayout(3, 3));
        add(controlPanel, BorderLayout.NORTH);

        controlPanel.add(new JLabel("Translate(dx,dy): "));

        sliderTransX = setSlider(controlPanel, JSlider.HORIZONTAL, 0, 300, 150,
            100, 50);
        sliderTransY = setSlider(controlPanel, JSlider.HORIZONTAL, 0, 300, 150,
            100, 50);

// To control rotation
        controlPanel.add(new JLabel("Rotate(Theta,ox,oy): "));
        sliderRotateTheta = setSlider(controlPanel, JSlider.HORIZONTAL, 0, 360,
            0, 90, 45);

        JPanel subPanel = new JPanel();
        subPanel.setLayout(new GridLayout(1, 2));

        sliderRotateX = setSlider(subPanel, JSlider.HORIZONTAL, 0, 300, 150,
            150, 50);

        sliderRotateY = setSlider(subPanel, JSlider.HORIZONTAL, 0, 300, 150,
            150, 50);
        controlPanel.add(subPanel);

// To control scaling
        controlPanel.add(new JLabel("Scale(sx,sy)x10E-2:"));

        sliderScaleX = setSlider(controlPanel, JSlider.HORIZONTAL, 0, 200, 100,
            100, 10);

        sliderScaleY = setSlider(controlPanel, JSlider.HORIZONTAL, 0, 200, 100,
            100, 10);

// To control width of line segments
        JLabel label4 = new JLabel("Width Control:", JLabel.RIGHT);
        sliderWidth = new JSlider(JSlider.HORIZONTAL, 0, 20, 1);
        sliderWidth.setPaintTicks(true);
        sliderWidth.setMajorTickSpacing(5);
        sliderWidth.setMinorTickSpacing(1);
        sliderWidth.setPaintLabels(true);
        sliderWidth.addChangeListener(new ChangeListener() {

            public void stateChanged(ChangeEvent e) {
                width = sliderWidth.getValue();
                canvas.repaint();
            }
        });
        JPanel widthPanel = new JPanel();
        widthPanel.setLayout(new GridLayout(1, 2));
        widthPanel.add(label4);
        widthPanel.add(sliderWidth);
        add(widthPanel, BorderLayout.SOUTH);

        canvas = new MyCanvas();
        add(canvas, "Center");
    }

    public JSlider setSlider(JPanel panel, int orientation, int minimumValue,
        int maximumValue, int initValue, int majorTickSpacing,
        int minorTickSpacing) {
        JSlider slider = new JSlider(orientation, minimumValue, maximumValue,
            initValue);
        slider.setPaintTicks(true);
        slider.setMajorTickSpacing(majorTickSpacing);
        slider.setMinorTickSpacing(minorTickSpacing);
        slider.setPaintLabels(true);
        slider.addChangeListener(new ChangeListener() {

            public void stateChanged(ChangeEvent e) {
                JSlider tempSlider = (JSlider) e.getSource();

                if (tempSlider.equals(sliderTransX)) {
                    transX = sliderTransX.getValue() - 150.0;
                    canvas.repaint();
                } else if (tempSlider.equals(sliderTransY)) {
                    transY = sliderTransY.getValue() - 150.0;
                    canvas.repaint();
                } else if (tempSlider.equals(sliderRotateTheta)) {
                    rotateTheta = sliderRotateTheta.getValue() * Math.PI / 180;
                    canvas.repaint();
                } else if (tempSlider.equals(sliderRotateX)) {
                    rotateX = sliderRotateX.getValue();
                    canvas.repaint();
                } else if (tempSlider.equals(sliderRotateY)) {
                    rotateY = sliderRotateY.getValue();
                    canvas.repaint();
                } else if (tempSlider.equals(sliderScaleX)) {
                    if (sliderScaleX.getValue() != 0.0) {
                        scaleX = sliderScaleX.getValue() / 100.0;
                        canvas.repaint();
                    }
                } else if (tempSlider.equals(sliderScaleY)) {
                    if (sliderScaleY.getValue() != 0.0) {
                        scaleY = sliderScaleY.getValue() / 100.0;
                        canvas.repaint();
                    }
                }
            }
        });
        panel.add(slider);

        return slider;
    }

    class MyCanvas extends Canvas {

        public void paint(Graphics g) {
            Graphics2D g2D = (Graphics2D) g;

            g2D.translate(transX, transY);
            g2D.rotate(rotateTheta, rotateX, rotateY);
            g2D.scale(scaleX, scaleY);

            BasicStroke stroke = new BasicStroke(width);
            g2D.setStroke(stroke);

            drawHome(g2D);
        }

        public void drawHome(Graphics2D g2D) {
            Line2D line1 = new Line2D.Float(100f, 200f, 200f, 200f);
            Line2D line2 = new Line2D.Float(100f, 200f, 100f, 100f);
            Line2D line3 = new Line2D.Float(100f, 100f, 200f, 100f);
            Line2D line5 = new Line2D.Float(200f, 100f, 200f, 200f);

            g2D.draw(line1);
            g2D.draw(line2);
            g2D.draw(line3);
            g2D.draw(line5);
        }
    }

    public static void main(String[] a) {
        JFrame f = new JFrame();
        f.getContentPane().add(new House());
        f.setDefaultCloseOperation(1);
        f.setSize(700, 550);
        f.setVisible(true);
    }
}

Please help me.

Answer 1

Don’t mix AWT and Swing components needlessly: extend JPanel and override paintComponent(). A call to super.paintComponent(g) will clean up rendering, and RenderingHints will improve rotated drawing.

class MyCanvas extends JPanel {

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2D = (Graphics2D) g;
        g2D.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);

        g2D.translate(transX, transY);
        g2D.rotate(rotateTheta, rotateX, rotateY);
        g2D.scale(scaleX, scaleY);

        BasicStroke stroke = new BasicStroke(width);
        g2D.setStroke(stroke);

        drawHome(g2D);
    }
...
}