LUA
  https://www.lua.org/license.html

fmt				
	https://github.com/fmtlib/fmt

spdlog			
	https://github.com/gabime/spdlog

nlohmann-json	
	https://github.com/nlohmann/json

freetype		
	https://freetype.org/

stb				
	https://github.com/nothings/stb

libtiff			
	http://www.libtiff.org/

Qt				
	https://www.qt.io/

tone mapping operator
  References:
  [1] Erik Reinhard and Kate Devlin, 'Dynamic Range Reduction Inspired by Photoreceptor Physiology',
  IEEE Transactions on Visualization and Computer Graphics, 11(1), Jan/Feb 2005.

