Display jpg in JPanel problem

[jimmy]

Hi All,

I am developing a GUI to display jpg images in a JPanel. I have
created two ways for the images to be selected: (i) a JFileChooser
button to select a single jpg, and (ii) a JFileChooser to select a
directory containing jpg files. Once the images have been selected,
they should be displayed on the JPanel.

In the case of opening the single file, this works as I hoped. However
when the open directory scenario is used, nothing is displayed.
Through the use of println statements I have been able to establish
the programme is executing the same Classes and Methods as in the
single image display. In addition to displaying an image, I have a
JLabel in which I display the name of the current image. Again for the
single image file selection, this works. For the open directory
scenario, only the name of the final image in the directory is
displayed (without the image).

Thinking that maybe there was not sufficient time for the image to be
displayed, I added a Thread.sleep(4000); line, but this did not help.

Included below are the two actionPerformed methods from each button,
plus the DrawImage and MyFilter Classes. I would appreciate if anyone
could indicate possible causes for the failure of the open directory
display method.

Many thanks,

Jimmy



BufferedImage image;
String filename;
DrawImage pic = null;

DrawImage pic2 = null;
String filename2;
BufferedImage image2 = null;

private void
openFileButtonActionPerformed(java.awt.event.ActionEvent evt)
{
JFileChooser chooser = new JFileChooser();
int returnVal = chooser.showOpenDialog(chooser);
if (returnVal == JFileChooser.APPROVE_OPTION) {
File file = chooser.getSelectedFile();
try {
image = ImageIO.read(file);
}
catch (IOException ex) {
System.out.println("There was a problem opening
the selected file: " + ex);
}

//mainImagePanel is the target JPanel for the image
Graphics g=mainImagePanel.getGraphics();

pic = new DrawImage();
pic.setImage(image);
pic.paintComponent(g);

//Add label text
filename = file.getPath();
jLabel1.setText(filename);
}
}

private void
openBatchButtonActionPerformed(java.awt.event.ActionEvent evt)
{

//JFileChooser to select a batch directory
JFileChooser chooserBatch = new JFileChooser();

chooserBatch.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);

int returnValBatch =
chooserBatch.showOpenDialog(chooserBatch);
File fileBatch = chooserBatch.getSelectedFile();

if (returnValBatch == JFileChooser.APPROVE_OPTION) {
System.out.println("Batch directory chosen: " +
fileBatch);
} else {
System.out.println("Error selecting batch directory: ");
}

//Get a file array of all jpgs in this directory
FilenameFilter only = new MyFilter("jpg");
File[] fileArray = fileBatch.listFiles(only);

//loop through jpg files
for (int i=0; i < fileArray.length; i++){

try {
image2 = ImageIO.read(fileArray);
} catch (IOException ex) {

Logger.getLogger(DesktopApplication3View.class.getName()).log(Level.SEVERE,
null, ex);
}
System.out.println("current file: " + fileArray);

//load image to main image panel
Graphics gg = mainImagePanel.getGraphics();
pic2 = new DrawImage();
pic2.setImage(image2);
pic2.paintComponent(gg);

//add filename to label
filename2 = fileArray.getPath();
jLabel1.setText(filename2);

}
}
/*****************************/
/*** Draw Main Image Panel ***/
/*****************************/

class DrawImage extends JPanel{

BufferedImage img;

public DrawImage() {
}

public void setImage(BufferedImage image){
this.img = image;
repaint();
}


@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
if(img != null) {
g2d.scale(0.2, 0.2);
g2d.drawImage(image, 0, 0, null);
}
else {
System.out.println("Image passed for drawing to main
panel is null");
}
}
}

/***********************/
/*** Filename Filter ***/
/***********************/

public class MyFilter implements FilenameFilter {

String ext;
public MyFilter(String ext) {
this.ext = "." + ext;
}
public boolean accept(File dir, String name) {
return name.endsWith(ext);
}
}

 

[John B. Matthews]

I am developing a GUI to display jpg images in a JPanel. I have
created two ways for the images to be selected: (i) a JFileChooser
button to select a single jpg, and (ii) a JFileChooser to select a
directory containing jpg files. Once the images have been selected,
they should be displayed on the JPanel.

Displayed how?

In the case of opening the single file, this works as I hoped.
However when the open directory scenario is used, nothing is
displayed. Through the use of println statements I have been able to
establish the programme is executing the same Classes and Methods as
in the single image display. In addition to displaying an image, I
have a JLabel in which I display the name of the current image. Again
for the single image file selection, this works. For the open
directory scenario, only the name of the final image in the directory
is displayed (without the image).

I suspect this has more to do with your (unseen) layout code. You might

Thinking that maybe there was not sufficient time for the image to be
displayed, I added a Thread.sleep(4000); line, but this did not help.

Invoking sleep() on the event dispatch thread is a bad idea.

Included below are the two actionPerformed methods from each button,
plus the DrawImage and MyFilter Classes. I would appreciate if anyone
could indicate possible causes for the failure of the open directory
display method.

[...]

 

[Knute Johnson]

Hi All,

I am developing a GUI to display jpg images in a JPanel. I have
created two ways for the images to be selected: (i) a JFileChooser
button to select a single jpg, and (ii) a JFileChooser to select a
directory containing jpg files. Once the images have been selected,
they should be displayed on the JPanel.

In the case of opening the single file, this works as I hoped. However
when the open directory scenario is used, nothing is displayed.
Through the use of println statements I have been able to establish
the programme is executing the same Classes and Methods as in the
single image display. In addition to displaying an image, I have a
JLabel in which I display the name of the current image. Again for the
single image file selection, this works. For the open directory
scenario, only the name of the final image in the directory is
displayed (without the image).

Thinking that maybe there was not sufficient time for the image to be
displayed, I added a Thread.sleep(4000); line, but this did not help.

Included below are the two actionPerformed methods from each button,
plus the DrawImage and MyFilter Classes. I would appreciate if anyone
could indicate possible causes for the failure of the open directory
display method.

Many thanks,

Jimmy



BufferedImage image;
String filename;
DrawImage pic = null;

DrawImage pic2 = null;
String filename2;
BufferedImage image2 = null;

private void
openFileButtonActionPerformed(java.awt.event.ActionEvent evt)
{
JFileChooser chooser = new JFileChooser();
int returnVal = chooser.showOpenDialog(chooser);
if (returnVal == JFileChooser.APPROVE_OPTION) {
File file = chooser.getSelectedFile();
try {
image = ImageIO.read(file);
}
catch (IOException ex) {
System.out.println("There was a problem opening
the selected file: " + ex);
}

//mainImagePanel is the target JPanel for the image
Graphics g=mainImagePanel.getGraphics();

pic = new DrawImage();
pic.setImage(image);
pic.paintComponent(g);

//Add label text
filename = file.getPath();
jLabel1.setText(filename);
}
}

private void
openBatchButtonActionPerformed(java.awt.event.ActionEvent evt)
{

//JFileChooser to select a batch directory
JFileChooser chooserBatch = new JFileChooser();

chooserBatch.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);

int returnValBatch =
chooserBatch.showOpenDialog(chooserBatch);
File fileBatch = chooserBatch.getSelectedFile();

if (returnValBatch == JFileChooser.APPROVE_OPTION) {
System.out.println("Batch directory chosen: " +
fileBatch);
} else {
System.out.println("Error selecting batch directory: ");
}

//Get a file array of all jpgs in this directory
FilenameFilter only = new MyFilter("jpg");
File[] fileArray = fileBatch.listFiles(only);

This is going to take longer than you want to spend on the EDT

//loop through jpg files
for (int i=0; i< fileArray.length; i++){

try {
image2 = ImageIO.read(fileArray);
} catch (IOException ex) {

Logger.getLogger(DesktopApplication3View.class.getName()).log(Level.SEVERE,
null, ex);
}
System.out.println("current file: " + fileArray);

You are creating new DrawImage here but not putting anywhere it can be
seen. Also, calling paintComponent() directly is probably not what you
want to do.

//load image to main image panel
Graphics gg = mainImagePanel.getGraphics();
pic2 = new DrawImage();
pic2.setImage(image2);
pic2.paintComponent(gg);

//add filename to label
filename2 = fileArray.getPath();
jLabel1.setText(filename2);

}
}

This looks OK.

/*****************************/
/*** Draw Main Image Panel ***/
/*****************************/

class DrawImage extends JPanel{

BufferedImage img;

public DrawImage() {
}

public void setImage(BufferedImage image){
this.img = image;
repaint();
}


@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D g2d = (Graphics2D)g;
if(img != null) {
g2d.scale(0.2, 0.2);
g2d.drawImage(image, 0, 0, null);
}
else {
System.out.println("Image passed for drawing to main
panel is null");
}
}
}

This ought to work too.

/***********************/
/*** Filename Filter ***/
/***********************/

public class MyFilter implements FilenameFilter {

String ext;
public MyFilter(String ext) {
this.ext = "." + ext;
}
public boolean accept(File dir, String name) {
return name.endsWith(ext);
}
}

Active rendering, calling paintComponent() directly is a useful and
quick method in some circumstances. I would however avoid doing that in
this case unless you are trying to create some sort of animation and
then your program needs to be redesigned to make it work correctly.

You should create an SSCCE, that will allow the list to give you better
advice.

 

[Daniel Pitts]

Hi All,

I am developing a GUI to display jpg images in a JPanel. I have
created two ways for the images to be selected: (i) a JFileChooser
button to select a single jpg, and (ii) a JFileChooser to select a
directory containing jpg files. Once the images have been selected,
they should be displayed on the JPanel.

In the case of opening the single file, this works as I hoped. However
when the open directory scenario is used, nothing is displayed.
Through the use of println statements I have been able to establish
the programme is executing the same Classes and Methods as in the
single image display. In addition to displaying an image, I have a
JLabel in which I display the name of the current image. Again for the
single image file selection, this works. For the open directory
scenario, only the name of the final image in the directory is
displayed (without the image).

Thinking that maybe there was not sufficient time for the image to be
displayed, I added a Thread.sleep(4000); line, but this did not help.

Included below are the two actionPerformed methods from each button,
plus the DrawImage and MyFilter Classes. I would appreciate if anyone
could indicate possible causes for the failure of the open directory
display method.

Many thanks,

Jimmy

Instead of drawing the image yourself, you should consider using
JLabel's "setIcon" method and an ImageIcon instance. It makes adding
images much easier, and is very flexible.

HTH.

 

[jimmy]

Thanks all for your help again. I didn't include the complete code for
my GUI as it was built using NetBeans and contains lots of other
buttons and panels, which were not relevant to the problem. I was
unaware of the SSCCE method of describing a problem, and I find it a
very good method. I did write an SSCCE example showing my problem, but
I fear that, as pointed out by Knute Johnson, the problems with my
code run deeper than the problem I described. I haven't fully grasped
how to work with images, therefore I am going to buy a book on Java
today (Head First Java seems to receive high praise) and spend some
time getting to grips with the basics.

Thanks Daniel Pitts for the JLabel suggestion, however I need to be
able to manipulate the images, which I believe is beyond the scope of
JLabel.

In the meantime I need to create a GUI for image analysis, so I have
started one in MATLAB (which I am much more familiar with than Java).
My intention is to create the final version in Java however.

Cheers,

Jimmy

 

[Knute Johnson]

Thanks all for your help again. I didn't include the complete code for
my GUI as it was built using NetBeans and contains lots of other
buttons and panels, which were not relevant to the problem. I was
unaware of the SSCCE method of describing a problem, and I find it a
very good method. I did write an SSCCE example showing my problem, but
I fear that, as pointed out by Knute Johnson, the problems with my
code run deeper than the problem I described. I haven't fully grasped
how to work with images, therefore I am going to buy a book on Java
today (Head First Java seems to receive high praise) and spend some
time getting to grips with the basics.

Thanks Daniel Pitts for the JLabel suggestion, however I need to be
able to manipulate the images, which I believe is beyond the scope of
JLabel.

In the meantime I need to create a GUI for image analysis, so I have
started one in MATLAB (which I am much more familiar with than Java).
My intention is to create the final version in Java however.

Cheers,

Jimmy

import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;

public class test extends JPanel {
private BufferedImage image;

public void setImage(BufferedImage bi) {
image = bi;
if (image != null) {
setPreferredSize(new Dimension(
bi.getWidth(),bi.getHeight()));
revalidate();
repaint();
}
}

public void paintComponent(Graphics g) {
super.paintComponent(g);
if (image != null)
g.drawImage(image,0,0,null);
}

public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
final JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final test t = new test();
JScrollPane sp = new JScrollPane(t);
f.add(sp,BorderLayout.CENTER);
JButton b = new JButton("Load Image");
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
JFileChooser chooser = new JFileChooser();
if (chooser.showOpenDialog(f) ==
JFileChooser.APPROVE_OPTION) {
try {
File file = chooser.getSelectedFile();
if (file.exists())
t.setImage(ImageIO.read(file));
} catch (IOException ioe) {
JOptionPane.showMessageDialog(f,ioe);
}
}
}
});
f.add(b,BorderLayout.SOUTH);
f.setSize(400,300);
f.setVisible(true);
}
});
}
}