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Ask Slashdot: How to catch Photoshop plagiarism

jemenake (595948) writes | about 2 years ago

Programming 4

jemenake (595948) writes "A friend of mine teaches electronic media (Photoshop, Premiere, etc.) at a local high-school. Right now, they're doing Photoshop, and each chapter in the book starts with an "end result" file which shows what they're going to construct in that chapter, and then, given the basic graphical assets (background textures, photos, etc.), the students need to duplicate the same look in the final-result file.

The problem, of course, is that some students just grab the final-result file and rename it and turn it in. Some are a little less brazen and they rename a few layers, maybe alter the colors on a few images, etc. So, it becomes time-consuming for her to open each file alongside the final-result file to see if it's "too perfect".

When I first discovered that she was doing this, my first reaction was that there's got to be some automated way of catching the cheaters. Of course, my first idea of just doing MD5 hashes of each file won't work, since most kids alter the file a little bit.

A second idea I had was to alter the final-result file in a way that isn't obvious, like removing someone's shoelace, mis-spelling a word in the background, or removing/adding some dust-specks. (I know map publishers and music transcribers use this trick to catch copiers). But this still requires that she look for the alteration in each file. I'd think that Photoshop, after all these years, would have some kind of scripting language which also supports some digital watermarking, but I've just never dabbled in that realm.

And, of course, I guess another solution would be for her to not provide the end-result file in Photoshop format, but to export it as a flat image. But I'm still intrigued by the notion of being able to "fuzzily" compare two photoshop files or images to find the ones which are too similar in certain aspects (color histograms, where the edges are, level of noise, whatever).

Anybody else have any clever ideas for this?"

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Years ago (0)

Anonymous Coward | about 2 years ago | (#41968907)

If your friend is on a Mac this can be accomplished via apple script. Dig around the forums and script libraries and you'll find one that can compare the pixels. It was about 5 years ago since I had to do this in a print production environment for version control of all things, running off a server

Re:Years ago (0)

Anonymous Coward | about 2 years ago | (#41970175)

It might be possible to use [] to do this for you? Upload the result images to their database, then compare to the student work?

Checksums? (0)

Anonymous Coward | about 2 years ago | (#41971363)

md5sum? Several graphics suites have CLI tools to manipulate images as well. It *should* be possible to extract and separate the resources within files then checksum or do direct comparisons as well.

Flatten it (1)

irbishop (1662375) | about 2 years ago | (#41971753)

If they just need to copy the look of the final image and they have all the instructions in the book then flatten the image, or save it without the layers. They can see what the end result looks like and if they turn in a file that doesn't show their work with layers they don't get credit.
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