Hello Anna, this happens on a quite old 7.8 debian wheezy. I tested it on a 8.2 jessie, and the problem is the same. No matter which driver from png or cairo is used. Would the problem rather be located on the wxpython layer ? Don't know if it can help : wx-config --version 3.0.2 python --version Python 2.7.3 Thanks for your attention ! Vincent.