NAME

video_displaygamma - get or set the gamma ramps for a display

SYNOPSIS

[tbl or boolean]
video_displaygamma( dispid or vid, tbl, index )

DESCRIPTION

Some hardware platforms and displays supports hardware accelerated gamma and color correction. This function is used to both test for the availability of such features and to change or query the currently active values. dispid is either 0 for the default display, or provided as a hotplug event in the applname_display_event handler. It is also possible to use a vid instead, if the connected client supports the extended color ramp subprotocol and has been granted permissions to synch such tables by setting the permission bit through target_flags TARGET_ALLOWCM . In this case, tbl may also contain an 'edid' key with the display ID , and the optional index (default=0) display subindex will be used. Clients that enable this feature will trigger the 'proto_change' event and may start generating 'ramp_update' events in the event of suggested ramp updates.

If the optional tbl argument is not set, the gamma tables will be queried, and returned as a number-indexed table with the individual channels (r, g, b) packed as separated planes (tbl[1] = r, tbl[#tbl/3] = g, tbl[#tbl/3*2] = b) as numbers in the 0.0 to 1.0 range.

If the optional tbl argument is set, the gamma tables for the display will be updated with new values and the function returns true or false depending on if the device accepted the tables or not. Mismatching tables may be a terminal state transition, so only use tables that come from a previous call to video_displaygamma .

EXAMPLE

function video_displaygamma0()
      local tbl = video_displaygamma(0);
      if (tbl and #tbl > 0) then
            for i=1,#tbl/3 do
                  tbl[i] = tbl[i] * 0.1;
            end
            video_displaygamma(0, tbl);
      else
            warning("display does not support gamma tables");
      end
end

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