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[java] Does ImageIO block?

Started by AbelCorver Feb 23, 2008 at 1:00 PM 4 replies 2.7k views

Original Post

Feb 23, 2008 at 1:00 PM

Hello, I'm trying to read several images from a JAR file. I created a method, which uses ImageIO.read(InputStream in) to read the image and it directly returns the result. This methods always returns null! This is very strange, because I tried the same thing with a ByteArrayInputStream and worked fine. I also tried a ZipInputStream, but nothing works! Does someone no what's going on? Thanks in advance.

Angex

Feb 23, 2008 at 2:36 PM

Since you can access the files using a byte stream the pathname is probably correct.

What format is the image you're trying to read?

By default only basic image types are supported, like; jpg, gif, png. You can check available formats using ImageIO.getReaderFormatNames()

OrangyTang

335

OrangyTang

Feb 23, 2008 at 2:46 PM

Have you checked that the input stream is valid? You want something like this.getClass().getClassLoader().getResourceAsStream(url) to get a stream to a resource inside a jar (assuming the jar is on the classpath).

AbelCorver

Author

AbelCorver

Feb 24, 2008 at 4:02 AM

No that's not the problem. ImageIO recognizes the image types (png and jpeg) if I use a ByteArrayInputStream, so why doesn't it work with a simple InputStream??

I don't use this.getClass().getClassLoader().getResourceAsStream(url), because the files are in another JAR file. But what's the difference between the ByteArrayInputStream and the normal InputStream?!?

Ichigo

Feb 24, 2008 at 5:26 AM

First of all InputStream is abstract so your probably using some unknown subclass of InputStream. Your problem might depend on what subclass it is.

It would probably help us if you posted some code to show how your getting this mysterious InputStream.

AbelCorver

Author

AbelCorver

Feb 25, 2008 at 3:37 AM

Maybe I found the problem. I read somewhere that ImageIO doesn't load the whole image. I think the image is loaded when you actually USE the image by drawing it somewhere. I call flush() on the BufferedImage, maybe that will help.

I'll send a reply if this worked.

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