GSoC/GCI Archive
Google Summer of Code 2012


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DIFFER (Determinator of Image File Format propERties) is an open source application which helps the user to understand the relationships between various file format properties, detect visual and non-visual errors and simplifies decision-making. An additional feature called compliance-check is designed to help us check the required specifications of the JPEG2000 file format.

This application supports selected still image formats:

  • JPEG/JFIF (*.jpe, *.jpeg),
  • JPEG2000 (*.jp2, *.jpf, *. jpx),
  • TIFF (*.tif, *.tiff),
  • DjVu, sDjVu (*.djv, *.djvu),
  • PNG (*.png)

with the maximum file size 15 MB. The selection was not random; it is based on needs of the Digital Preservation Standard Department at the National Library in the Czech Republic.

Identification, validation, and characterization actions are frequently necessary during routine operation of digital repositories and for digital preservation activities. We use for these actions different existing tools and modules:


In addition, DIFFER includes the following open source libraries:


The project DIFFER is built in order to implement only open-source tools and modules. The whole wrapper is intended for free use and is itself an open-source.

The DIFFER should be part of the workflow of digitization of the national heritage of the Czech Republic. If you want to work on real problems and help with preserving cultural heritage, continue to our ideas page.




  • Multithreaded implementation of new similarity metrics (image data) into existing framework. The functionality of project Differ is not only validation and identification of still image file formats, but also the ability to compare two different image files and processing of such comparison. For this purposes we would like to Implementation of the new ways of comparing two different image files and improving upon their execution times by utilizing multi-threaded programming. Some of such comparison metrics are, namely, SSIM (Structural Similarity), PSNR (Peak Signal to Noise ratio, MSSIM and "A Universal Image Quality Index".