Given that it is a common stimulus in visual science, I was wondering whether someone has already the code to generate such a stimulus.
The code below does it. Note that, for the code below, the radius below is the confusing bit. Here’s an explanation:
It’s units are “fractions of the stimulus” in this case and the radius is specified to 3xSigma (for the gaussian). SO if you have a stimulus width of 3 deg (so radius of 1.5) then setting the filter radius to be 0.1 means that the radius was actually 0.1*3/2 = 0.15 deg = 3xSigma. So if you want to quote the gaussian filter in terms of its sigma (common practice) it would be radiusXstimSize/2/3 = 0.05 deg in this case.
Here’s the code to create it:
from psychopy import filters import numpy as np from psychopy import visual, event def makeFilteredNoise(res, radius, shape='gauss'): noise = np.random.random([res, res]) kernel = filters.makeMask(res, shape=shape, radius=radius) filteredNoise = filters.conv2d(kernel, noise) filteredNoise = (filteredNoise-filteredNoise.min())/(filteredNoise.max()-filteredNoise.min())*2-1 return filteredNoise filteredNoise = makeFilteredNoise(256, 0.1) win = visual.Window([400,400], monitor='testMonitor') stim = visual.ImageStim(win, image = filteredNoise, mask=None) stim.draw() win.flip() event.waitKeys()
Thanks for the code. This is Gaussian smoothing, isn’t it? I ll try to modify it to obtain a bandpass.
Oh sorry yes I misread your request. Bandpass filtering needs to be done in the fourier domain so a bit different.
@jon already gave a nice answer for generating static images. If you want a moving image or the possibility to control bandwidth in the orientation domain, you may be interested in the code :
This easily generates images or movies and has been already suite extensively used with psychopy. As @jon mentioned, this is al done in the Fourier space.
Just stumbled onto this code. Thanks Jon!
Mysteriously, I can’t seem to get this to work with a units=“pix” window. The numpy array looks reasonable, but drawing an ImageStim where image is set to this seems to draw nothing.