[solved] Unnecessary picture resize in sketchpad?

Comments

• LeeB_86

  October 2013 edited 3:39AM

  Have you set the experiment resolution (on the 'General Overview') to match the screen you are using? I found that to be a problem in a recent experiment of mine when I switched to using a different screen.

  Best,

  Lee
• sebastiaan

  October 2013 edited 3:39AM

  PsychoPy's PatchStim and GratingStim classes convert images to rectangular patches of power-of-two dimensions. This is required for technical reasons. You generally don't notice this, but at the pixel level things may go slightly wrong. For example, very thin lines may disappear or become vague.

  If there is no specific reason to use the psycho back-end, you could try switching to the xpyriment back-end. Alternatively, you could present the image using PsychoPy's ImageStim class, in an inline_script item. The ImageStim class is somewhat newer and from what I understand it works slightly differently, so it may prevent the distortion from occurring.

  • http://www.psychopy.org/api/visual/imagestim.html

  Hope this helps!

  Cheers,
  Sebastiaan

  
  
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• Papi

  October 2013 edited 3:39AM

  Hey Lee, thanks for your suggestions, but the resolution already matches the screen resolution, so that is not the reason.

  Sebastiaan, alas there is a reason why the xpyriment bachend does not work for me: I use Ascii asterisks as cues fin the eyperiment (like this ✱). These asterisks are displayed when I use the PsychoPy backend, but not when I use the xpyriment backend. If you know a way how to present asterisks in xpyriment, that would be very useful for me then (I guess as images they would work).

  Thanks already!
• LeeB_86

  October 2013 edited 3:39AM

  but the resolution already matches the screen resolution, so that is not the reason.

  ... I guess I'm the only one making goofy mistakes then!

  Hope it works out, back-end issues are beyond my knowledge...

  Lee
• Papi

  October 2013 edited 3:39AM

  certainly not, the same thing happened to me at least once, but now the resolution is correct ;-)
• sebastiaan

  October 2013 edited 3:39AM

  I use Ascii asterisks as cues fin the eyperiment (like this ✱)

  Right, that's quite an exotic character you have there! This asterisk is actually not an ASCII character (this one is: *), which is why it is not shown by the xpyriment back-end: It's simply not part of the default font. If you can find out which font does include this character, you should be able to view it as well with the xpyriment back-end. So I would simply try a few different fonts until the character appears.

  You can quickly create a script that tries a lot of different fonts, like so:

  draw textline 0 0 "✱" font_family="Times New Roman"
  draw textline 100 0 "✱" font_family="Arial"
  draw textline 200 0 "✱" font_family="Courier New"
  # etc.
  

  
  
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• Papi

  October 2013 edited 3:39AM

  Hi Sebastiaan,

  I tried quite some fonts, but all resulted in an empty square instead of the asterisk. This seems odd to me, because the asterisk works in all fonts in the PsychoPy backend.

  I just created an image to display the asterisk, that works fine, thanks anyway!!