Screen(‘ReadNormalizedGammaTable’)

Psychtoolbox>Screen.{mex*} subfunction

Reads and returns the gamma table ‘gammatable’ of the specified screen or window
‘windowPtrOrScreenNumber’.
Returns the output resolution of the video DAC as optional second argument
‘dacbits’. Will return dacbits=8 as a safe default if it is unable to query the
real resolution of the DAC. Currently only OS-X reports the real DAC size. Will
return the real number of slots in the hardware lookup table in optional return
argument ‘reallutsize’. Currently only OS-X and Linux report the real LUT size.
On MacOS-X, the optional ‘physicalDisplay’ flag can be set to 1, zero is the
default. In this case, the ‘windowPtrOrScreenNumber’ argument (which then must
be a real screen number, not a window index) selects among physically present
display devices, instead of logical devices. This is important if you want to
assign different gamma-tables to multiple displays in a ‘clone’ or ‘mirror mode’
configuration, as there is only one logical display, but multiple physical
displays, mirroring each other. Please note that screen numbering is different
for physical vs. logical displays. For a list of physical display indices, call
Screen(‘Screens’, 1);
On GNU/Linux, the optional ‘physicalDisplay’ parameter selects the video output
from which the gamma table should be read in multi-display mode. On Linux a
screen can output to multiple video displays, therefore this parameter allows to
query the individual gamma tables for each display. The default setting is -1,
which means to read the gamma table of the primary output of the given screen.
See help for Screen(‘LoadNormalizedGammaTable’); for infos about the format of
the returned table and for further explanations regarding gamma tables.

###See also: