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Thread: Super-imposing images by making background transparent (case 429)

  1. #1
    Join Date
    May 2012
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    Super-imposing images by making background transparent (case 429)

    I need to super-impose two polygons, one polygon on top of another. To do this, I need to make the background transparent. This can be done for a pgn file, but apparently DirectRT cannot take pgn files.

    A possibility would be to do the super-imposition outside of DirectRT, but the polygons are made of 2 sets of 30, which would require pre-randomization of 900 trials.

    I would be grateful for any advice.
    Last edited by jason_reed; 05-06-2015 at 04:51 PM.

  2. #2
    Join Date
    Nov 2005
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    3,323
    That's tricky because DirectRT does not currently support transparency. You could possibly do this in MediaLab--do you have access to it? And what are the timing requirements--e.g., are subjects reacting with keyboard response to each combination, or are they simply viewing them and then responding later on? With MediaLab, a custom item could likely be set up to present the combinations using HTML--a context that would support the transparency requirements. Just a thought. But again, I can't see a quick work-around in DirectRT short of, as you suggested, the rather tedious task of pre-combining the combinations as single stimuli.

  3. #3
    Join Date
    May 2012
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    The subjects are reaction with keyboard responses to each combination and RTs are being measured as the dependent variable.
    I'm not familiar with mediaLab--would it indeed be possible?

  4. #4
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    Are you expecting a fairly uniform RT collection, such as 500-1000ms with some minor variation? Or something like 1000-5000ms with a relatively large variation in RTs?

  5. #5
    Join Date
    May 2012
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    Hi
    More like 500-1000ms with some variation

  6. #6
    Join Date
    Feb 2013
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    1,094
    Please let me know if you need further assistance with this matter.
    Jason Reed
    Empirisoft Software Support Specialist

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