Verifying that an Image is Valid
In my application, I am loading in a user specified image to be used as an icon.
My code works fine, except in the case where an image file is invalid.
i.e. You change the file extension on some random file to ".jpg", and try to load it.
The program doesn't crash or throw any exceptions, it simply imports without problem, and displays a blank image whenever I try to display the image.
What I need is some way to verify that an image is corrupt/invalid before continuing.
Here is the simple code that selects the image:
publicclass SelectImageActionextends AbstractAction{
privatestaticfinallong serialVersionUID = 1;
public SelectImageAction(){
super("Select...");
}
publicvoid actionPerformed (ActionEvent evt){
if (imageFileChooser ==null){
imageFileChooser =new JFileChooser();
imageFileChooser.setFileFilter(new FileFilter(){
publicboolean accept(File file){
if (file.isDirectory()){
returntrue;
}
else{
String fn = file.getName();
if (fn.endsWith(".jpg") || fn.endsWith(".JPG") ||
fn.endsWith(".gif") || fn.endsWith(".GIF") ||
fn.endsWith(".png") || fn.endsWith(".PNG")){
returntrue;
}
returnfalse;
}
}
@Override
public String getDescription(){
return"Image File";
}
});
}
imageFileChooser.showOpenDialog(ManageServiceCenterDialog.this);
if (imageFileChooser.getSelectedFile() !=null){
int useImage = JOptionPane.YES_OPTION;
//TODO: IF IMAGE IS INVALID: SHOW ERROR MESSAGE AND REPEAT METHOD
if (currentImage !=null){
useImage = JOptionPane.showConfirmDialog(ManageServiceCenterDialog.this,
"Attaching a new image will clear current image, would you like to proceed?",
"Clear Current Image?", JOptionPane.YES_NO_OPTION);
}
if (useImage == JOptionPane.YES_OPTION){
String imagePath = imageFileChooser.getSelectedFile().getAbsolutePath();
currentImage =new ImageIcon(imagePath).getImage();
}
}
}
}
If I've been unclear in any way, or you need more information, please don't hesitate to ask.
# 1
Figured it out.
A few other small changes made as well.
public class SelectImageAction extends AbstractAction {
private static final long serialVersionUID = 1;
public SelectImageAction() {
super("Attach...");
}
public void actionPerformed (ActionEvent evt) {
if (imageFileChooser == null) {
imageFileChooser = new JFileChooser();
imageFileChooser.setFileFilter(new FileFilter() {
public boolean accept(File file) {
if (file.isDirectory()) {
return true;
}
else {
String fn = file.getName();
if (fn.endsWith(".jpg") || fn.endsWith(".JPG") ||
fn.endsWith(".gif") || fn.endsWith(".GIF") ||
fn.endsWith(".png") || fn.endsWith(".PNG")) {
return true;
}
return false;
}
}
@Override
public String getDescription() {
return "Image File";
}
});
}
int retval =
imageFileChooser.showOpenDialog(SomeDialog.this);
if (retval == JFileChooser.APPROVE_OPTION) {
int useImage = JOptionPane.YES_OPTION;
String imagePath = imageFileChooser.getSelectedFile().getAbsolutePath();
Image image = new ImageIcon(imagePath).getImage();
//Load the image and check if it is valid.
MediaTracker mt = new MediaTracker(SomeDialog.this);
mt.addImage(image, 1);
boolean imagesuccess = true;
try {
mt.waitForID(1);
} catch (InterruptedException e) {
imagesuccess = false;
}
imagesuccess = imagesuccess & !mt.isErrorID(1);
if(imagesuccess)
{
if (currentImage != null) {
useImage = JOptionPane.showConfirmDialog(SomeDialog.this,
"Attaching a new image will clear current image, would you like to proceed?",
"Clear Current Image?", JOptionPane.YES_NO_OPTION);
}
if (useImage == JOptionPane.YES_OPTION) {
currentImage = image;
}
} else {
JOptionPane.showMessageDialog(SomeDialog.this,
"The selected image is corrupt or not recognized.\nPlease select another image.",
"Invalid Image", JOptionPane.ERROR_MESSAGE);
actionPerformed(evt);
}
}
}
}
# 2
Some files will throw exceptons if you
attempt to load them as images using
Java 1.6.
For the ones that don't, you might try using the
PixelGrabber to get a random clutch of points
from around the image, and compare the RGB
values of those points.
If the RGB values are identical in the sample,
it is a good sign that the image is blank, and
therefore corrupt (or very boring!).
