Error with Gamma Correction in Psychopy

Question

I'm trying to gamma correct my computer monitor using an OceanOptics Spectrometer to gather the data and Pyschopy's gamma correction module to linearize the curve.

The program appears to work around 4/5 times but will occasionally give me an error when I attempt to setGammaRamp. I was just what the error might be. Is it possible that it is a problem with 32-64 bit conversion using ctypes? Here's the error that I get:

Traceback (most recent call last):
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\Lib\site-packages\aibs\chrisgammatest.py", line 139, in <module>
    Calib=GammaTest()
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\Lib\site-packages\aibs\chrisgammatest.py", line 22, in __init__
    self.monitorcal()
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\Lib\site-packages\aibs\chrisgammatest.py", line 81, in monitorcal
    sample=self.gammaTest()
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\Lib\site-packages\aibs\chrisgammatest.py", line 42, in gammaTest
    window=visual.Window(units='norm',monitor=monitortype, fullscr = True, screen = screennumber, waitBlanking=True)
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\psychopy\visual.py", line 334, in __init__
    self.setGamma(self.gamma)#using either pygame or bits++
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\psychopy\visual.py", line 935, in setGamma
    self.winHandle.setGamma(self.winHandle, self.gamma)
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\psychopy\gamma.py", line 34, in setGamma
    setGammaRamp(pygletWindow, newLUT)
  File "C:\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\psychopy\gamma.py", line 51, in setGammaRamp
    success = windll.gdi32.SetDeviceGammaRamp(pygletWindow._dc, newRamp.ctypes)
ctypes.ArgumentError: argument 1: <type 'exceptions.OverflowError'>: long int too long to convert

Answer 1

There seems to be a 32/64 sign extension problem on GetDC() in ctypes / Pyglet / Psychopy.

See: https://github.com/psychopy/psychopy/issues/504

It also appears that Windows doesn't allow all gamma settings, see: http://jonls.dk/2010/09/windows-gamma-adjustments/