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Education Graphics Programming

Ask Slashdot: How To Catch Photoshop Plagiarism? 284

First time accepted submitter jemenake 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.'" How to look for images closer than they should be to the original? Read on for more details.
jemenake continues: "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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Ask Slashdot: How To Catch Photoshop Plagiarism?

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  • by Anonymous Coward on Tuesday November 13, 2012 @02:33PM (#41970889)

    Paste images into the source image as new layers, adjust layer mode to "difference" and look for the similarities. Done.

  • Instead (Score:4, Interesting)

    by Sparticus789 ( 2625955 ) on Tuesday November 13, 2012 @02:37PM (#41970965) Journal

    She could also not show the students a picture of the final project. She could just give them a list like:

    1. Remove one set of shoelaces.
    2. Add a bird in the sky
    3. Add a portrait of Spock in the background.

  • Re:simple solution (Score:4, Interesting)

    by ColdWetDog ( 752185 ) on Tuesday November 13, 2012 @03:00PM (#41971393) Homepage

    This should work and would be trivial to do.

    If you want to spend more time on it, make sure that the student's copy of Photoshop is set to record history in the metadata.

    Then you can go through and look at every step they made. I do this on some images so I can figure out what the hell I did to get that effect three years later. It takes up little space - it's just text.

    But a more boring way to spend a day would be hard to create.

  • Re:Simple Solution (Score:3, Interesting)

    by Anonymous Coward on Tuesday November 13, 2012 @03:06PM (#41971463)

    "If they can't do it at the end, they will fail. If they didn't ask for help, tough. Treat them like adults. They will ether rise to it or learn what doesn't work."

    While that is a fair approach, I've found that I get much higher success rates in the end if I have some kind of feedback during the period they are working. If they don't *know* they're way off track, or don't *know* they aren't putting in enough effort, then, sure, they'll fail at the end like they should, but there will be some missed opportunities where honest and interested students would have increased their effort had they realized the course demanded more.

    Inevitably, there will be some students that are incorrigible. I can't do much for those. But a mid-term "reality check" evaluation worth, say, half as much as the final evaluation, is really useful. It also means that students who don't want to put in the required effort can bail out early (which means I don't have to waste my time with them the rest of the term either -- a win-win as far as I'm concerned).

  • by mrbene ( 1380531 ) on Tuesday November 13, 2012 @03:08PM (#41971505)

    It's probably annoying for all involved, but just like the "show your work" in math classes, you can request a "show your work" equivalent via screen-cast. And the students will learn a bit about screen-casting.

    Alternatively, request a picture of each step.

  • by tlambert ( 566799 ) on Tuesday November 13, 2012 @03:46PM (#41972155)

    Why does this sound like a stock image supplier trying to find machine-modified infringing images using a web crawler so that they can bludgeon the people publishing the modified images, who have not paid a license fee, with a copyright infringement lawsuit?

    I'm just saying, a good answer to the OP's question is going to mean the ability to use the answer in this fashion.

  • by tverbeek ( 457094 ) on Tuesday November 13, 2012 @06:55PM (#41974853) Homepage

    Let them use their own base images! And then let them do something creative with them!

    One of the least interesting and least creative classes I took in art school was one that was about producing photorealistic oil paintings based on photographs. The class was 99% about mechanical technique, and to hell with creativity... which seems to be the theme of the class being taught here. So be it. But at least the instructor let us pick our own photographs to replicate! So we'd have an interest in what we were doing. And even if he had never checked on our progress along he way (like would happen in any worthwhile "learn how to ____" class), he would know whether we had done the work, because each of our paintings was a) unique, and b) matched the photograph we'd had approved at the start of the assignment. Plagiarism wasn't even a question, and not just because we were working in traditional physical media.

    All of these suggestions for how to identify plagiarism through technological measures are missing the point. The problem isn't "how to catch a cheat", but "how to give students an assignment that they will have a reason to bother doing in the first place".

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