wxPython Image brightness control and changing between wximage, bitmap and PIL

wxPython Image brightness control and changing between wximage, bitmap and
PIL

I'm programming a gui and is looking for a method to control the
brightness of my image using a slider. i've tried using ConvertToGreyscale
but it is not giving what i want since images are in RGB and
ConvertToGreyscale is in YUV.
i know that PIL have a lot of capabilities for images processing but i
will have to convert between wximage, bitmap and PILimage. tried looking
at http://wiki.wxpython.org/WorkingWithImages but solutions there doesn't
seem to be working.
assistance is greatly appreciated.