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video_displaygamma(3)		  Arcan Lua API 	   video_displaygamma(3)

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 availabil-
     ity 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 subproto-
     col 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  fea-
     ture  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

SEE ALSO:
vidsys				   August 2026		   video_displaygamma(3)

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<https://man.freebsd.org/cgi/man.cgi?query=video_displaygamma&sektion=3&manpath=FreeBSD+Ports+15.1.quarterly>

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