Saturday, May 19, 2012

A simple JP2 file structure checker.

A simple JP2 file structure checker. Johan van der Knijff. Open Planets.
One major risk of file migration is that hardware failures during the migration process may result in corrupted images. Ideally JHOVE would be able to detect such errors using format validation tools.  "I started out with removing some trailing bytes from a lossily compressed JP2 image. As it turned out, I could remove most of the image code stream (reducing the original 2 MB image to a mere 4 kilobytes!), but JHOVE would still say the file was "well-formed and valid". I was also able to open and render these files with viewer applications such as Adobe Photoshop, Kakadu's viewer and Irfanview. The behaviour of the viewer apps isn't really a surprise, since the ability to render an image without having to load the entire code stream is actually one of the features that make JPEG 2000 so interesting for many access applications. JHOVE's behaviour was a bit more surprising, and perhaps slightly worrying." So he wrote a very simple JP2 file structure checker that is available for download.


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