Load the hardware color lookup table (CLUT) of a video screen. It uses
Screen(‘LoadCLUT’), as appropriate, to leave the hardware CLUT
containing the numbers you provide in “clut”, with no transformation.
There *are* restrictions: On Microsoft Windows you can’t use CLUTs for
animation, as the operating system requires all CLUTs to contain mono-
tonically increasing entries. Psychtoolbox currently has no way of
detecting the resolution of your graphics cards DAC, so unless you
explicitly provide the DAC resolution in the optional parameter ‘bits’,
it will always assume a 8-Bit DAC. This assumption is safe, but it does
not allow you to automatically take advantage of higher resolution DACs.
Apart from that, all pixelSizes are supported. It should works with all
graphics cards on MacOS-X, Windows and Linux. Fully supports 8-or-more-bit
We *strongly* suggest that all users use Screen(‘LoadNormalizedGammaTable’)
in new code. Its values range between 0.0 and 1.0 and are independent
of DAC size, the system automatically maps the range 0.0 - 1.0 to the
range really available on your graphics card, so no need for you (or for
Psychtoolbox) to know the resolution of your graphics cards DAC. You will
always automatically benefit from the highest possible resolution of your
The err return argument is only here for backwards compatibility to
the old Psychtoolbox. It always will be empty.
“clut”, the user-supplied color table, should be a clutSizex3 matrix.
Each row in the “clut” matrix is loaded into an RGB entry in the
hardware CLUT. The values of the matrix elements should be integers in
the range 0 to 2^bits-1.
The maximum clut size is 256 rows, but you can pass less rows if you only
want to change a portion of the hardware CLUT.
“startEntry” is optional and determines which hardware CLUT entry to
load first. Entries are numbered from 0 up. The default is 0. The first
element of “clut”, i.e. clut(1), will be loaded into hardware entry
“bits” specifies how many bits you want to write to the CLUT. Typically
it will be 8 bits, which is the default value. If you set it to
some other value, the range of allowable entries scales accordingly.
Thus if you use a 10-bit CLUT, then each entry should be between 0 and
GRAPHICS CARDS WITH MORE-THAN-8-BIT DACS:
See also Screen subfunctions ‘LoadCLUT’, ‘LoadNormalizedGammaTable’,