How to check if the file is an image

Question

I want to check if the file passed is an image and if not I want to show a message indicating that the file is not an image .

try{
    Image img = ImageIO.read(new File(name));
}catch(IOException ex)
{
    valid=false;
    System.out.println("The file" + name + "could not be opened, it is not an image");
}

When the file (referenced by name) is not an image valid is not set to false, why is this happening? Should I change the type of the exception? I have read about the try-catch, and as I understand if ImageIO.read fails and the type of the exception is IOException contents of catch block will be executed. So why its not executed ?

Is there is any other way to check if the file is an image??

This link will be useful to you : http://stackoverflow.com/questions/9643228/test-if-file-is-an-image — Ruby, Aug 13 '13 at 12:06

score 32 · Accepted Answer · edited Apr 13 '16 at 11:33

32

According to the Javadocs, read returns null if the file can not be read as an image.

If no registered ImageReader claims to be able to read the resulting stream, null is returned.

So, your code should be the following:

try {
    Image image = ImageIO.read(new File(name));
    if (image == null) {
        valid = false;
        System.out.println("The file"+name+"could not be opened , it is not an image");
    }
} catch(IOException ex) {
    valid = false;
    System.out.println("The file"+name+"could not be opened , an error occurred.");
}

edited Apr 13 '16 at 11:33

KlimczakM

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answered Aug 13 '13 at 11:58

Brent Worden

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I think this is the right approach but it's no error free. Take a look to [this](http://stackoverflow.com/questions/18079754/convert-and-display-image-from-byte-array?noredirect=1#comment26495118_18079754). In this case `ImageIO` couldn't read image files even when those files actually were images. – dic19 Aug 13 '13 at 12:07

score 5 · Answer 2 · edited Oct 07 '17 at 20:09

5

According to API ImageIO.read(...) returns null if no registered ImageReader able to read the specified file is found, so you can simply test returned result for null.

edited Oct 07 '17 at 20:09

MWiesner

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answered Aug 13 '13 at 12:00

Evgeniy Dorofeev

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Brent Worden was faster. But you are right :) – Martijn Courteaux Aug 13 '13 at 12:01
that is why I voted up both answers and accepted his answer ^^ – Alaa Aug 13 '13 at 17:28

score 1 · Answer 3 · edited Oct 07 '17 at 20:10

1

Use this to get the extension:

String extension = "";

int i = fileName.lastIndexOf('.');
if (i > 0) {
    extension = fileName.substring(i+1);
}

And check the conditions as u want

if(extension=="jpg"){
//your code
}

and so on

edited Oct 07 '17 at 20:10

MWiesner

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answered Aug 13 '13 at 11:54

Hybrid Developer

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What if i change the extension of an image from .jpeg to .mpeg? – ihsan kocak Aug 13 '13 at 11:56
I am not sure this will always works. An extension can be changed or can be absent. – VirtualTroll Aug 13 '13 at 11:56
1

What if there is no extension at all? Shouldn't that cause a problem here? As far as I know, the correct way is to check for the mime type. – MD Sayem Ahmed Aug 13 '13 at 11:56
2

Usually images do not a have extensions like .mpeg or .wmv – Hybrid Developer Aug 13 '13 at 11:58
but it do have extension like .jpeg or .png or .gif etc – Ruby Aug 13 '13 at 12:03
2

Use `extension.equals("")` instead of `==`. see this question: [**How do I compare strings in Java?**](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java). – Azad Aug 13 '13 at 12:16
@Azad: You are right... – Hybrid Developer Aug 13 '13 at 12:18

How to check if the file is an image

3 Answers3