I'm trying to make flickering images (4 stimuli that will flicker in a different rate)
One thing I've noticed is that when using regular text (for instance letters) the size of the masking shape has to be bigger than the stimuli (the text size is set by fontstyle with percentage of screen size, background colour is transparent) in a factor of 1.35. For some reason, the width is completely overlapped but there are some variation with hight. (please see enclosed the debugger window). So there is still some portion of the text that is not covered by the mask.
I had to increase the size of the mask by a factor of 1.31 in order to cover fully the stimuli.
Here is a short example:
/1 = "o" //primary
/2 = "o" //secondary
/3 = "o" //always
/ items = item.shapeItems
/ txcolor = black
/ txbgcolor = transparent
/ select = list.aShapePrimaryLow.nextvalue
/ color = parameters.globalScreenColor
/shape = rectangle
/ size = (text.flickerSimLow_1.widthpct*values.multBlankStimRatio_w, text.flickerSimLow_1.heightpct*values.multBlankStimRatio_h)
/ position = (text.flickerSimLow_1.hposition, text.flickerSimLow_1.vposition)
============================End example ========================================
Note that even though the percentage is the same, pixel-wise they are not.
Changing the mask shape to be as the same pixels of the text does not help either.
Originally the flickering was made by these text shapes "⚫", "▲", ""◼", but due to the problem I've changed it to be 4 stimuli that are the same and the problem still exist.
Any idea why this happens and would it be the same for pictures?