Python crashes at the end of experiment: Image.open

IngerMat · April 2018

Hey everyone,

I am really new to OpenSesame and I am experiencing a problem. I have to write some inline script but OpenSesame keeps crashing at the end of every experiment. I have deduced that the problem is with the Image.open function from PIL. Does anyone know how to fix this?

Kind regards,
Inger

        from PIL import Image
        from math import hypot

        ## Preload mouse
        my_mouse = mouse()
        ## Preload canvas
        my_canvas = canvas(exp)
        star = exp.pool[u'star5.png'] 
        src = exp.get_file('star5.png') 
        my_canvas.image(star)
        img = Image.open(src)

IngerMat · April 2018

Also this is the message I get in the debug window

experiment.run(): experiment finished at Thu Apr 26 19:26:29 2018
experiment.end(): enabling garbage collection
done!

Python seems to have crashed. This should not happen. If Python crashes often, please report it on the OpenSesame forum.

item-stack: 
time: Thu Apr 26 19:26:30 2018

sebastiaan · April 2018

Hi Inger,

This error indicates that the Python interpreter itself crashes, rather than that there's a bug in your script per se. That being said, your script is a bit funny, because you're opening the same image twice. What exactly are you trying to do?

Cheers!
Sebastiaan

IngerMat · April 2018

Thanks for the feedback! Is there any way to make sure that the Python does not crash?

I open the image twice because they have two different purposes. My task involves participants moving around the mouse and me having the know the color of the pixel that the mouse location is on. If the mouse is on the white part of the image, black part, etc.

So the purpose of the first image (var star) is to display the image on the canvas and the second image (var img) is to be able to backtrack the color of the pixel because you need to use PIL Image for that.

sebastiaan · May 2018

Thanks for the feedback! Is there any way to make sure that the Python does not crash?

It's a bug in Python itself, or in one of the low-level libraries. So no, not really, except indirectly by avoiding the situation that causes Python to crash.

I open the image twice because they have two different purposes. My task involves participants moving around the mouse and me having the know the color of the pixel that the mouse location is on. If the mouse is on the white part of the image, black part, etc.

I suspect that the crash may occur because the file is not immediately closed by OpenSesame, and then if you open it again with Image.open() it causes some kind of conflict. That's my best guess in any case.

What I would do is first open the image and load it into a numpy array with scipy.misc.imread(). You can then get the pixel colors from this array.

https://docs.scipy.org/doc/scipy-0.18.1/reference/generated/scipy.misc.imread.html

This will (or should) immediately close the image file again, and then you can use Canvas.image() again without having the same file open twice.

Does that help?

IngerMat · May 2018

Dear Sebastiaan,

Thank you for your remark. The problem was indeed due to that the image of with the PIL function did not close properly. I worked around it by calling Image.close() which seems to be doing the trick! I figured it out before seeing your remark, but I assume that your solution would work as well.

Kind regards,
Inger

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