Psychtoolbox>Screen.{mex*} subfunction

[gammatable, dacbits, reallutsize] = Screen(‘ReadNormalizedGammaTable’, windowPtrOrScreenNumber [, physicalDisplay]);

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=0 as a “Don’t know” value if it is unable to
query the real resolution of the DAC. Currently no operating system reports a
trustworthy ‘dacbits’.
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: