Thursday, December 29, 2011

JPEG Snoop

I posted this to ImpulseAdventure's site to ask a question about JPEGSnoop: "Take a photo with your camera. Upload it to Facebook. Download it from Facebook. Run the downloaded image through JPEGSnoop.

The software will show it as edited. Essentially, Facebook recompresses the image on your computer before it uploads it to their servers. Gone are the markers from your camera.

Other than the recompress - there's no actual "editing" as most people use the term. Nothing added or deleted to the photo.

What are your thoughts on this? Is it possible to refine the terms? Something like this could be listed as double quantization - resaved? How about a DCT histogram to point to the integrity of the image in spite of the double quantization?

Here's their response:
"You're absolutely right Jim... The term "edited" is used very loosely. Really, all that is meant is "not-original". As it is incredibly hard to differentiate simple resaving (recompression) from an edit+resaving, I haven't made any efforts to report "double quantization". I'm definitely open to ideas on suitable terminology. Of course most people are interested in determining if an image has been altered in the more general sense of the word (ie. modified to misrepresent reality), rather than simple resaving, resizing, etc. Regarding the DCT histogram, what type of data were you thinking could be interesting from a histogram perspective? Thanks!"

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