Safe to update separate regions of a BufferedImage in separate threads?

Posted by finnw on Stack Overflow See other posts from Stack Overflow or by finnw
Published on 2010-05-18T12:47:31Z Indexed on 2010/05/18 12:51 UTC
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java

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bufferedimage

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multithreading

I have a collection of BufferedImage instances, one main image and some subimages created by calling getSubImage on the main image. The subimages do not overlap. I am also making modifications to the subimage and I want to split this into multiple threads, one per subimage.

From my understanding of how BufferedImage, Raster and DataBuffer work, this should be safe because:

Each instance of BufferedImage (and its respective WritableRaster) is accessed from only one thread.
The shared ColorModel is immutable
The DataBuffer has no fields that can be modified (the only thing that can change is elements of the backing array.)
Modifying disjoint segments of an array in separate threads is safe.

However I cannot find anything in the documentation that says that it is definitely safe to do this. Can I assume it is safe? I know that it is possible to work on copies of the child Rasters but I would prefer to avoid this because of memory constraints.

Otherwise, is it possible to make the operation thread-safe without copying regions of the parent image?

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