DC: Shoot the file – Image corruption

In the first lab session of Digital Curation, Amy, Taylor, Colm and I experimented with a tool simulating the ageing and corruption of digital files.

We mainly manipulated the image formats gif and jpg. By applying a set of parameters of shooting and corrupting, we noticed how the visuals of the images changed considerably and the images became increasingly difficult to interpret.

 

The file originally looked like this:

thaller_image_-historic_doc
(1) Original image

 

At first, we  ‘shot’ the jpg file three times:

  • at 100 bytes -> 215 sequences of 100 bytes
  • at 50 bytes -> 127 sequences of 54 bytes
  • at 1 byte-> 55 sequences of 1 byte

In the resulting picture, the handwritten notes and their table structure are still recognisable, but the whole image is blurred.

thaller_image_-historic_doc
(2) Shot jpg image

 

After corrupting the original jpg file three times, the output is substantially more distorted than above. This lead us to the assumption that the corruption of images has a more severe impact than the shooting.

thaller_image_-historic_doc-2
(3) Corrupted jpg image

 

We also corrupted a gif three times using the same parameters as above. Now, the image is almost totally black and no longer indicates to the original content. It could therefore be possible that gifs are less stable image formats than jpgs. Yet, this assumption would have to be verified with further corruption attempts.

thaller_image_-historic_doc-1
(4) Corrupted gif image

 

 

Interestingly, I have noticed that when opening the corrupted files on my mac, the images show slightly different distortions than the ones I had saved earlier on my Windows account in the lab. I assume this discrepancy exemplifies the instability of jpg and gif files once they have been corrupted.

And take a look at image 4 displayed in bigger size; do you see the difference?

thaller_image_-historic_doc-1
(5) Image 4 enlarged
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