Image onto JFrame

tedds · #1 23-Oct-2007, 21:07

Hello I am starting an app to import an image, it imports an image ok when it i hard coded. I am trying to provide a name for the image in main, using args[0], but I keep getting a "Exception in main()java.lang.NullPointerException". is this because the args parameter is not getting used by the paint method?

cheers

tedds

JAVA Code:

import java.awt.*;
import javax.imageio.*;
import java.awt.image.*;
import java.io.*;
import javax.swing.*;
import javax.swing.border.TitledBorder;
import java.awt.event.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.filechooser.*;

class TestImage extends JFrame
{

  ImagePanel theImagePanel;
  
  private String args;
  private String DEFAULT_FILE_IMAGE = args;
  private final int X_POSITION = 10;
  private final int Y_POSITION = 40;
  
  private JButton selectFileButton;
  
  private JButton upsideDownButton;
  private JButton cycleColorsButton;
  private JButton reduceRedButton;
  private JButton reduceSizeButton;
  private JButton saveToFileButton;
  
  public static File fDirectory = null;
  

  public TestImage(String theTitle)
  {
   super(theTitle);  
      
   theImagePanel = new ImagePanel();
     
   JPanel buttonPanel = new JPanel();
   buttonPanel.setLayout(new FlowLayout());
   buttonPanel.setBorder(BorderFactory.createEtchedBorder(Color.red, Color.red));
   
   selectFileButton = new JButton("Open File");
   buttonPanel.add(selectFileButton);  
    
   JPanel functionPanel = new JPanel();
   functionPanel.setLayout(new FlowLayout());
   functionPanel.setBorder(BorderFactory.createEtchedBorder(Color.red, Color.red));
   
   upsideDownButton = new JButton("Upside Down");
   cycleColorsButton = new JButton("Cycle Color");
   reduceRedButton = new JButton("Reduce Red");
   reduceSizeButton = new JButton("Reduce Size");
   saveToFileButton = new JButton("Save");
   functionPanel.add(upsideDownButton);
   functionPanel.add(cycleColorsButton);
   functionPanel.add(reduceRedButton);
   functionPanel.add(reduceSizeButton);
   functionPanel.add(saveToFileButton);
   
   //add listener to buttons
   selectFileButton.addActionListener(new SelectFileListener());
   upsideDownButton.addActionListener(new FlipImageListener());
   cycleColorsButton.addActionListener(new CycleColorListener());
   reduceRedButton.addActionListener(new ReduceRedListener());
   reduceSizeButton.addActionListener(new ReduceSizeListener());
   saveToFileButton.addActionListener(new SaveFileListener());
   
   
   //text area to add messages to
   JTextPane messageTextPanel = new JTextPane();
   
   //set up scoll affect
   JScrollPane scroll = new JScrollPane(messageTextPanel);
   //set message panel fort properties
   messageTextPanel.setFont(new Font("MS Sans Serif", 1, 14));
   //place a border around the whole panel
   scroll.setBorder(BorderFactory.createEtchedBorder(Color.red, Color.red));
   //place a border around the inner message panel and give it a title
   messageTextPanel.setBorder(new TitledBorder("Messages"));
   //position whole panel on the screen and set size
   scroll.setBounds(480,45,300,475);

   //add panels to main JFrame
   getContentPane().add(scroll);
   getContentPane().add("North",buttonPanel);
   getContentPane().add(theImagePanel);
   getContentPane().add("South",functionPanel);

  }
  
  /**
   * This class blah blah blah
   */
  class SelectFileListener implements ActionListener
  {

    public void actionPerformed(ActionEvent e)
    {
        
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        //image.flipX();
        //System.out.print("Select file button pressed");
        
        /*
        JFileChooser chooser = new JFileChooser();
        chooser.setBackground(Color.blue);
        if(fDirectory != null)
        chooser.setCurrentDirectoy(fDirectory);
        */
        
        ///*
        JFileChooser chooser = new JFileChooser();  
        
        FileReader in = null;
        if (chooser.showOpenDialog(null) == JFileChooser.APPROVE_OPTION)
        {
            File selectedFile = chooser.getSelectedFile();
            String path = selectedFile.getPath();
            System.out.println(path);
            Image DEFAULT_FILE_IMAGE = new Image(path);
            
            if (!selectedFile.exists())
            {
                System.out.println(image + " does not exists");
            }
            //getContentPane().add(new image(newImage));
            //reader = new fileReader(selectedFile);
        }
        //*/
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
              //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new SelectFileListener();
      selectFileButton.addActionListener(listener);
    }
  }
  
  /**
   * This class blah blah blah
   */
  class FlipImageListener implements ActionListener
  {

      JTextPane messageTextPanel;// = new JTextPane();
    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        image.flipX();
        System.out.println("Flip button pressed");
        //messageTextPanel.replaceSelection("Flip button pressed");
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new FlipImageListener();
      upsideDownButton.addActionListener(listener);
      //return upsideDownButton;
    }

  }
  
  /**
   * This class blah blah blah
   */
  class CycleColorListener implements ActionListener
  {

      JTextPane messageTextPanel;// = new JTextPane();
    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        //image.flipX();
        System.out.println("Cycle color button pressed");
        //messageTextPanel.replaceSelection("Flip button pressed");
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new CycleColorListener();
      cycleColorsButton.addActionListener(listener);
      //return upsideDownButton;
    }

  }
  
  /**
   * This class blah blah blah
   */
  class ReduceRedListener implements ActionListener
  {

      JTextPane messageTextPanel;// = new JTextPane();
    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        //image.flipX();
        System.out.println("Reduce red button pressed");
        //messageTextPanel.replaceSelection("Flip button pressed");
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new ReduceRedListener();
      reduceRedButton.addActionListener(listener);
      //return upsideDownButton;
    }

  }
  
  /**
   * This class blah blah blah
   */
  class ReduceSizeListener implements ActionListener
  {

      JTextPane messageTextPanel;// = new JTextPane();
    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        //image.flipX();
        System.out.println("Reduce size button pressed");
        //messageTextPanel.replaceSelection("Flip button pressed");
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new ReduceSizeListener();
      reduceSizeButton.addActionListener(listener);
      //return upsideDownButton;
    }

  }
  
  /**
   * This class blah blah blah
   */
  class SaveFileListener implements ActionListener
  {

      JTextPane messageTextPanel;// = new JTextPane();
    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(DEFAULT_FILE_IMAGE);
        //image.flipX();
        System.out.println("Save file button pressed");
        //messageTextPanel.replaceSelection("Flip button pressed");
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }
      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new SaveFileListener();
      saveToFileButton.addActionListener(listener);
      //return upsideDownButton;
    }

  }
  
  /**
   * This class ImagePanel is where the image is set
   */
  
  class ImagePanel extends JPanel //or JFrame
  {
      
  public void paint(Graphics g)
  {
      try {
      // Read the image
      Image image = new Image(args);

      // Display the image
      image.draw(g, X_POSITION,Y_POSITION);
      
      // Flip the image upside down
      image.flipX();
      // Draw the flipped image
      
   // image.draw(g, X_POSITION + (image.getWidth()*2),Y_POSITION);
      image.draw(g, X_POSITION ,Y_POSITION);
      //image.write("horseNew.jpg");
        }
      catch (Exception e) 
      {
        System.out.println("Exception in main()" + e.toString());
      }

  }
}
  public static void main(String args[])
        throws java.io.IOException, java.io.FileNotFoundException
    {
               if (args.length != 1)
       {
         System.err.println(
           "Please include image filename on command line");
         System.exit(-1);
       }
       
    // Read
    Image image = new Image(args[0]);
    System.out.println(args[0]);
   
    TestImage.setDefaultLookAndFeelDecorated(true);
    TestImage testimage = new TestImage("Test Image"); 
    testimage.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    testimage.setVisible(true);
    testimage.setPreferredSize(new Dimension(800, 600));
    testimage.setResizable(false);
    testimage.pack();
    
    //Center the main frame
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension size = testimage.getSize();
    screenSize.height = screenSize.height/2;
    screenSize.width = screenSize.width/2;
    size.height = size.height/2;
    size.width = size.width/2;
    int y = screenSize.height - size.height;
    int x = screenSize.width - size.width;
    
    //set location from x and y settings
    testimage.setLocation(x, y);

  }
}

TurboPT · #2 24-Oct-2007, 09:26

Yes, 'args' IS null at the paint method, for in the TestImage class, 'args' is declared, but never assigned anything -- so it is null.

How does that code work for you? The Image class is abstract, and compiling gives this:

Code:

C:\TestImage.java:103: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:123: java.awt.Image is abstract; cannot be instantiated
Image DEFAULT_FILE_IMAGE = new Image(path);
                           ^
C:\TestImage.java:155: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:156: cannot find symbol
symbol  : method flipX()
location: class java.awt.Image
image.flipX();
     ^
C:\TestImage.java:183: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:211: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:239: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:267: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(DEFAULT_FILE_IMAGE);
              ^
C:\TestImage.java:295: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(args);
              ^
C:\TestImage.java:298: cannot find symbol
symbol  : method draw(java.awt.Graphics,int,int)
location: class java.awt.Image
image.draw(g, X_POSITION,Y_POSITION);
     ^
C:\TestImage.java:301: cannot find symbol
symbol  : method flipX()
location: class java.awt.Image
image.flipX();
     ^
C:\TestImage.java:305: cannot find symbol
symbol  : method draw(java.awt.Graphics,int,int)
location: class java.awt.Image
image.draw(g, X_POSITION ,Y_POSITION);
     ^
C:\TestImage.java:326: java.awt.Image is abstract; cannot be instantiated
Image image = new Image(args[0]);
              ^
13 errors

Anyway, since 'args' is NOT global from main(), you can pass the desired 'args' value from main through a TestImage constructor, maybe something like this:

JAVA Code:

public TestImage(String theTitle, String theImagePath) // 2-arg constructor.
{
  args = theImagePath; // assign the 'args' value in the TestImage class.
  TestImage(theTitle); // keep the original constructor for initialization.
}

Note that this is just one possible solution. There are many ways to solve the problem.

tedds · #3 24-Oct-2007, 09:36

Thats not good, I should have said that I have a class "Image". Thank you for your response, i changed the constuctor and it worked, so i have quickly gone onto creating a JFileChooser.
I just added a JFileChooser to my code, so that when the app is running you can click the button to choose a different file. I can see how I can allocate the new pic to a brand new frame by duplicating the main method and creating a new JFrame. Is there a way that I can use the selected file from JFileChooser and replace the original file from args[0]?

cheers

JAVA Code:

public void actionPerformed(ActionEvent e)
    {
        
        JFrame f = new JFrame();
        JFileChooser jFileChooser1 = new javax.swing.JFileChooser();
        f.addWindowListener(new java.awt.event.WindowAdapter()
        {
            public void windowClosing(java.awt.event.WindowEvent evt)
            {
                System.exit(0);
            }
        });
        java.awt.Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
        f.setLocation((screenSize.width-500)/2,(screenSize.height-300)/2);  
        int returnVal = jFileChooser1.showOpenDialog(f);
        if (returnVal == jFileChooser1.APPROVE_OPTION)
        {
            File fi = new File(jFileChooser1.getSelectedFile().getPath());
            String path = fi.getPath();
            System.out.println(path);
            ImageIcon icon = new ImageIcon(path);
 
            TestImage testimage = new TestImage("fileload", fi.getParent()+"/"+fi.getName());
 
//this puts an image on a new JFrame
     /*       
    testimage.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    
    testimage.setVisible(true);
    testimage.setPreferredSize(new Dimension(800, 600));
    testimage.setResizable(false);
    testimage.pack();
    */
 
       }

TurboPT · #4 24-Oct-2007, 09:49

If there's a way to get the file string from the JFileChooser, I would think it would be a simple of matter of reassigning the 'args' variable with the file string -- if that it what you mean.

Note: I made a minor edit in post #2.

tedds · #5 24-Oct-2007, 09:54

yep, thats what I had in mind. Im going to give that a go now. I just have to make sure the args[0] in the main method still don't override the new file string.

cheers

yep it worked a charm, excatly what you mentioned

thank you for your time, its good to learn from not just books.

cheers

tedds · #6 24-Oct-2007, 10:46

hello again, im going pretty quick through what to do with this swing stuff. the Image class has a method of flipX(), which turns the image upside down. I am trying to use this method and see if I can in fact change the image. I think that this is similar to the last issue that I had, but I'm not to sure. Do you how I can do this?

cheers

JAVA Code:

  class FlipImageListener implements ActionListener
  {

    public void actionPerformed(ActionEvent e)
    {
        try
        {
        Image image = new Image(theImage);
        
        image.flipX();

        TestImage testimage = new TestImage("Flipped Image", theImage);
  
    }
        catch (java.io.IOException exception)
        {
            exception.printStackTrace();
        }

      //add lisnter to flip to allow for turning image upside down
      ActionListener listener = new FlipImageListener();
      upsideDownButton.addActionListener(listener);
    }

  }

tedds · #7 25-Oct-2007, 18:04

Hello TurboPT, thanks for your advice on the previous. I have come back to this and am checking out how to cycle through the rbg colors of a loaded image. for example, the red takes the blue value, blue takes the green value and green takes the red value. I ave stated the method for this, but am stuck on how to get the rbg values from the array. I am assuming that after the second for loop, I find the rbg values then assign them, i.e. r(value) = b(value), b(value) = g(value), g(value) = r(value). Am I making a correct assumption here?

Cheers

Code:

  public void cycleColor() {
      
    Color newRgbColor;  
    for (int row = 0; row < height; row++) {
      for (int col = 0; col < width; col++) {
        newRgbColor = picture[row][col];
        picture[row][col] = newRgbColor;
      }
    } 
    
  }

TurboPT · #8 25-Oct-2007, 19:48

There is a getRGB() function (as well as other 'get' functions for specific, individual [Red,Green,Blue] colors) is this what you need?

Unfortunately, I haven't done much with color-space stuff, so my help might be limited here.

tedds · #9 25-Oct-2007, 20:04

Yeah thats what I need, I've just been reading up about it and it looks like I can figured it out.
Thanks for the response.

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