BF: Fixes filtered noise issue

Fixes tounding error in noise.py which was slightly altering the spatial frequency composition of Butterworth filtered noise and 'filtered' noise samples and doing so differenly for PY2 and PY3.
psychopy · May 13, 2019 · 5d0e360 · 5d0e360
1 parent b669eab
commit 5d0e360
Showing 1 changed file with 6 additions and 6 deletions.
diff --git a/psychopy/visual/noise.py b/psychopy/visual/noise.py
@@ -16,7 +16,7 @@
 # up by the pyglet GL engine and have no effect.
 # Shaders will work but require OpenGL2.0 drivers AND PyOpenGL3.0+
 
-from __future__ import absolute_import, print_function
+from __future__ import absolute_import, print_function, division
 
 import pyglet
 pyglet.options['debug_gl'] = False
@@ -495,8 +495,8 @@ def _filter(self, FT):
                                                             cutoff_y = self._upsf / filterSize, 
                                                             n=self.noiseFilterOrder, 
                                                             alpha=0, 
-                                                            offset_x = 2 / (filterSize-1),
-                                                            offset_y = 2 / (filterSize-1))
+                                                                offset_x = 0.5/filterSize,  #becuase FFTs are slightly off centred.
+                                                                offset_y = 0.5/filterSize)
             else:
                 filter = numpy.ones((int(filterSize),int(filterSize)))
             if self._lowsf > 0:
@@ -509,8 +509,8 @@ def _filter(self, FT):
                                                                 cutoff_y = self._lowsf / filterSize, 
                                                                 n = self.noiseFilterOrder, 
                                                                 alpha = 0, 
-                                                                offset_x = 2/(filterSize - 1),
-                                                                offset_y = 2/(filterSize - 1))
+                                                                offset_x = 0.5/filterSize, #becuase FFTs are slightly off centred.
+                                                                offset_y = 0.5/filterSize)
             return FT * filter
         else:
             return FT
@@ -691,7 +691,7 @@ def buildNoise(self):
         if not(self.noiseType in ['binary','Binary','normal','Normal','uniform','Uniform']):
             if (self.noiseType in ['filtered','Filtered']) or (self.filter in ['butterworth', 'Butterworth']):
                 self.noiseTex=self._filter(self.noiseTex)
-            elif (self.noiseType in ['Isotropic','isotropic']) or (self.filter in ['isotropic', 'Isopropic']):
+            elif (self.noiseType in ['Isotropic','isotropic']) or (self.filter in ['isotropic', 'Isotropic']):
                 self.noiseTex = self._isotropic(self.noiseTex)
             elif (self.noiseType in ['Gabor','gabor']) or (self.filter in ['gabor', 'Gabor']):
                 self.noiseTex = self._gabor(self.noiseTex)