Cannot change Gabor patch size
Hello opensesame wizards,
I'm trying to create Gabor patches with a certain size. However, for some strange reason the value I add to the 'size=' variable doesn't seem to have any effect. For example, the code:
pre_canvas.gabor(-100, 0, angle, .025, size=200)
pre_canvas.gabor(100, 0, angle, .025, size=400)
...gives me two identical Gabor patches. No matter what I do, the size remains the same.
I'm using a PsychoPy backend, and running OpenSesame 3.2.5 (I tried it on a different version, and got the same problem unfortunately).
Any clues?
Many thanks in advance,
Jasper de Waard
Comments
Hi Jasper,
Not sure why (maybe intentional, maybe a bug), but the size keyword doesn't do anything if you use a gaussian envelope on your grating. To manipulate the size, you have to instead change the "stdev" keyword. For Gaussian Gabors, size is defined as 6* the stdev. see here (function: _mask): https://github.com/smathot/OpenSesame/blob/koffka/openexp/_canvas/_element/psycho.py
Eduard
@sebastiaan, if this intentional, we should update the documentation; if not, we should fix it.
Hi Eduard,
Thanks, that's very enlightening!
Cheers, Jasper
Hi guys,
Thanks for pointing this out. The meaning of the
sizekeyword is indeed a bit confusing. Strictly speaking, the size of a gabor patch is infinite, and thestdevkeyword just indicates how quickly the patch fades away, so to say. But practically speaking, there's of course an image with a finite size, and that's what thesizeargument refers to, except that for the psycho backend the size is chosen so large that the patch always looks infinite. (I don't recall why, to be honest.)Long story short: I'll update the docs to clarify this!
Cheers,
Sebastiaan