AffineTransform rotate+resize+center

Question

I have an image in landscape format. This image should be rotated 90 degrees (into portrait format) then resized to fit screen (by height) and finally centered on the screen. I'll like to use AffineTransform to do this task, but I cannot figure out have to make the translation so the picture is centered on the screen.
What is needed to make the following code work?
import java.awt.*;
import java.io.*;
import javax.swing.*;
import java.awt.geom.*;
public class RotateAndResize extends JFrame
     public static Image image;
     public static void main(String[] args) throws Exception
          //A photo (in landscape format) which need to be rotated 90 degress (to portrait format)
          File thumbFile = new File("C:\\...\\P1080309.jpg");
          image = javax.imageio.ImageIO.read(thumbFile);
          RotateAndResize frame = new RotateAndResize();
          frame.setSize(800,600);
          frame.setVisible(true);
     public void update ( Graphics g )
            paint(g);
     public void paint(Graphics in)
          Graphics2D g = (Graphics2D) in;
          int w = getWidth();
          int h = getHeight();
          int imgWidth = image.getWidth(null);
          int imgHeight = image.getHeight(null);
          g.setColor (new Color(0,0,0));
          g.fillRect (0,0,w,h);
          //switch due to rotation
          int tmp = imgHeight;
          imgHeight = imgWidth;
          imgWidth = tmp;               
          double scale = Math.min((double)w/imgWidth, (double)h/imgHeight);
          AffineTransform at = AffineTransform.getScaleInstance(scale, scale);
          at.quadrantRotate(1); //90
          g.setTransform ( at );
          g.drawImage(image
                         ,w/2 - imgWidth / 2 //center
                         ,h/2 - imgHeight / 2 //center
                         ,imgWidth
                         ,imgHeight
                         ,null);               
}

Answer 1

First and foremost:
1. Always create and show Swing components on the EDT using SwingUtilities (or EventQueue) #invokeLater.
2. Never draw to a JFrame, it's a top level container and is meant to hold other components. Do custom painting in a JCompoent or JPanel subclass. See [the Tutorial|http://java.sun.com/docs/books/tutorial/uiswing/painting/index.html].
3. Your GUI is not a special type of JFrame and should not subclass JFrame. Always prefer composition over inheritance.
Is this an exercise to use AffineTransform? I usually find it easier to work with the Graphics2D API.import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class LandscapeToPortrait {
   Image image;
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         @Override
         public void run() {
            new LandscapeToPortrait().makeUI();
   public void makeUI() {
      try {
         // change the filename to your image file
         image = ImageIO.read(new File(
               "E:/TestImage.jpg"));
         // scale to screen size, landscape mode
         image = image.getScaledInstance(800, 600, Image.SCALE_SMOOTH);
      } catch (IOException ex) {
         ex.printStackTrace();
      JPanel panel = new JPanel() {
         @Override
         protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (image != null) {
               int imageWidth = image.getWidth(null);
               int imageHeight = image.getHeight(null);
               int panelWidth = getWidth();
               int panelHeight = getHeight();
               double scale = (double) panelHeight / imageWidth;
               Graphics2D g2 = (Graphics2D) g.create();
               // translate to the center of the panel
               g2.translate(panelWidth / 2, panelHeight / 2);
               // rotate 90°
               g2.rotate(Math.PI / 2);
               // translate to the point where the top-right of the
               // image should paint.  Remember that when rotated 90°,
               // +x -> +y and +y -> -x
               // [0,5]            [0,0]
               //   +----------------+
               //   |                |
               //   |                |
               //   |                |
               //   |                |
               //   |                |
               //   |                |
               //   |                |
               //   +----------------+
               // [5,5]             [5,0]
               // Also remember that the image will be scaled when painted
               g2.translate(-panelHeight / 2, -imageHeight * scale / 2);
               // apply the scale
               g2.scale(scale, scale);
               g2.drawImage(image, 0, 0, this);
               g2.dispose();
      panel.setPreferredSize(new Dimension(400, 400));
      JFrame frame = new JFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setContentPane(panel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
}db