 On some operating systems running the X Window System, one can set the gamma correction factor (applied to the existing gamma value) by issuing the command codice_1 for setting gamma correction factor to 0.9, and codice_2 for querying current value of that factor (the default is 1.0).In macOS systems, the gamma and other related screen calibrations are made through the System Preferences.The test image is only valid when displayed "raw", i.e.