After some investigation it looks like dispose() needs to be called on 
ImageReaders and ImageWriters after using them. The methods affected would be 
net.coobird.thumbnailator.tasks.io.InputStreamImageSource.read()
net.coobird.thumbnailator.tasks.io.OutputStreamImageSink.write(BufferedImage)
net.coobird.thumbnailator.tasks.io.FileImageSource.read()
net.coobird.thumbnailator.tasks.io.FileImageSink.write(BufferedImage)

Hi,

Thank you for taking your time to report this issue.

It does appear like there are many instances of people encountering 
`OutOfMemoryError`s when using Thumbnailator with Java 7 Update 21.

The need to address this issue has been acknowledged.

Issue 44 appears to be the same issue.

I've also gotten a report of a memory leak via an e-mail from Vladimir Shomin 
on April 24.

Quote:

> I have discovered some memory problem due exploiting system, when thousands of
> images have queued for thumbnailation - application server tomcat-7.0.39
> under jdk-1.7.0_21 crushes with OutOfMemoryError.
>
> Exploring heap state with VisualVM tool, I have found that memory is filled
> by megabyte-sized byte[] objects that linked as root by
> com.sun...JPEGImageReader . Forums recommend to use BufferedImage.dispose()
> and ImageReader.flush() methods beyond image processing cause its releases
> low-level resources used within image manipulations.

Again, this appears to occur when using Java 7 Update 21, which is the most 
up-to-date version of Java available as of the time of writing this comment.

Therefore, this issue should be given the highest priority.

Issue 44 has been merged into this issue.

Reproducing the Problem
-------------------------

In an effort to reproduce the problem, I ran a variation of the following code:

  Thumbnails.of(new File("/path/to/images").listFiles()
    .scale(0.1)
    .toFiles(new ConsecutivelyNumberedFilenames(new File("/path/for/thumbnails")));

I set the JVM's maximum heap settings to `-Xmx96m`, as that was the easiest 
value to see the Java 1.7.0_21 JVM to throw an `OutOfMemoryError` while 
processing images.

Using Thumbnailator 0.4.3 with the above settings, Java 1.7.0_21 would throw an 
`OutOfMemoryError` after processing 15 JPEGs which had the dimensions of 3648 x 
2736 pixels.

In contrast, when running with the same settings on Java 1.7.0_4, an 
`OutOfMemoryError` did not occur.


Attempting a Fix
-------------------------

As pointed out by the issue reporters, the problem probably lies in the lack of 
disposal code for the `ImageReader`s and `ImageWriter`s.

First, the disposal of the `ImageReader`s in the `FileImageSource` and 
`InputStreamImageSource` classes were added.
However, after running the test code, it encountered an `OutOfMemoryError` at 
15 images; the same as last time.

Next, the disposal of the `ImageWriters`s in the `FileImageSink` and 
`InputStreamImageSink` classes were added.

The results this time was that the test code would run without encountered an 
`OutOfMemoryError`.
(The code was subsequently changed to output to PNG, and the results were the 
same -- no `OutOfMemoryError`.)

As an added measure, a call to `BufferedImage.flush` has been added to the 
`Thumbnailator.createThumbnail(ThumbnailTask<?, ?>)` method, which should free 
up some resources as well.


Current Status
-------------------------

Thumbnailator 0.4.4 which addresses this `OutOfMemoryError` issue should be 
ready (hopefully) by the end of the week.

The changes has been pushed to the repository under the `0.4.4` branch:
http://code.google.com/p/thumbnailator/source/browse/?name=0.4.4

All unit tests are passing at this point, but I'll perform some manual testing 
before release.

Issue 46 is similar issue (though that may not mean the cause is similar). 
Please take a look as well.

Issue 46 is for jdk 1.6 build 45.

I have reproduced the problem with Thumbnailator 0.4.3 running on Java 6 Update 
45.

When running the candidate for Thumbnailator 0.4.4 on Java 6 Update 45, it does 
not exhibit the `OutOfMemoryError` problem.

I'll merge Issue 46 into this issue.

Issue 46 has been merged into this issue.

Issue 45 has been merged into this issue.

This issue has been resolved in Thumbnailator 0.4.4.

I'd like to thank everyone involved in resolving this issue for contributing 
your time and effort! :)

was this a bug in a particular jdk version? was there a commit that fixed it? 
just wondering

No bug in the jdk, just a bug in Thumbnailator where resources weren't being 
cleaned up. It only seemed to matter in more recent jdk versions which were 
doing some optimizations by re-using resources (assuming they'd be disposed of 
when necessary)